System and method for resetting a reaction mass assembly of a stage assembly

ABSTRACT

A stage assembly for moving and positioning a device is provided herein. The stage assembly includes a stage base, a stage, a stage mover assembly, a reaction mass assembly, a reaction mover assembly, and a control system. The stage mover assembly moves the stage relative to the stage base. The reaction mass assembly reduces the reaction forces created by the stage mover assembly that are transferred to the stage base. The reaction mover assembly adjusts the position of the reaction mass assembly relative to the stage base. Uniquely, the control system controls and directs current to the reaction mover assembly in a way that minimizes the influence of disturbances created by the reaction mover assembly on the stage assembly. More specifically, the timing and/or the amount of current from the control system directed to the reaction mover assembly is varied to minimize the influence of the disturbances created by the reaction mover assembly on the stage assembly. With this design, the reaction mover assembly has less influence upon the position of the stage base. This allows for more accurate positioning of the device by the stage assembly and better performance of the stage assembly.

This application is a continuation-in-part of U.S. patent applicationSer. No. 09/714,598, now abandoned filed Nov. 16, 2000, and of U.S.patent application Ser. No. 09/739,772, filed Dec. 20, 2000, nowabandoned, the entire disclosures of which are incorporated herein byreference.

CROSS REFERENCE TO RELATED APPLICATIONS

As far as permitted, the disclosures of (i) U.S. patent application Ser.No. 09/714,747, entitled, “STAGE ASSEMBLY INCLUDING A REACTION MASSASSEMBLY,” filed on the same day as the present Application, (ii) U.S.patent application Ser. No. 09/713,911, entitled “STAGE ASSEMBLYINCLUDING A REACTION ASSEMBLY,” filed on the same day as the presentApplication, and (iii) U.S. patent application Ser. No. 09/713,910,entitled “STAGE ASSEMBLY INCLUDING A REACTION ASSEMBLY THAT IS CONNECTEDBY ACTUATORS,” filed on the same day as the present Application, areincorporated herein by reference.

BACKGROUND OF THE INVENTION

1. Field of Invention

The present invention is directed to a stage assembly for moving adevice. More specifically, the present invention is directed to a stageassembly including a reaction mass assembly and a system and method forresetting the reaction mass assembly. The present invention also relatesto an exposure apparatus and method, and more particularly to anexposure apparatus and method for transferring a pattern onto asubstrate by irradiation of an exposure beam.

2. Description of Related Art

Various types of exposure apparatus are conventionally used inphotolithographic processes for manufacturing semiconductor devices,liquid crystal display devices, and the like. In recent years, astep-and-repeat reduction projection exposure apparatus (a so-called“stepper”), a step-and-scan scan-exposure apparatus (a so-called“scanning stepper”), and the like have been widely used.

Exposure apparatuses are commonly used to transfer images from a reticleonto a semiconductor wafer during semiconductor processing. A typicalexposure apparatus includes an illumination source, a reticle stageassembly that retains a reticle, a lens assembly and a wafer stageassembly that retains a semiconductor wafer. The reticle stage assemblyand the wafer stage assembly are supported above a ground with anapparatus frame.

Typically, the wafer stage assembly includes a wafer stage base, a waferstage that retains the wafer, and a wafer stage mover assembly thatprecisely positions the wafer stage and the wafer. Somewhat similarly,the reticle stage assembly includes a reticle stage base, a reticlestage that retains the reticle, and a reticle stage mover assembly thatprecisely positions the reticle stage and the reticle. The size of theimages transferred onto the wafer from the reticle is extremely small.Accordingly, the precise relative positioning of the wafer and thereticle is critical to the manufacturing of high density, semiconductorwafers.

Unfortunately, the wafer stage mover assembly generates reaction forcesthat can vibrate the wafer stage base and the apparatus frame. Thevibration influences the position of the wafer stage base, the waferstage, and the wafer. As a result thereof, the vibration can cause analignment error between the reticle and the wafer. This reduces theaccuracy of positioning of the wafer relative to the reticle anddegrades the accuracy of the exposure apparatus. Reaction forcesproduced due to driving of the wafer stage is mechanically caused toescape to the floor (the ground) by a frame member placed on a base(e.g., a floor surface or a base plate of the apparatus) which isvibration-isolated from the stage, as disclosed in, for example, U.S.Pat. No. 5,528,118.

In the case of the scanning stepper, a reticle stage as well as a waferstage needs to be driven in a predetermined scanning direction by alinear motor or the like. In order to absorb reaction forces produceddue to driving of the reticle stage, a countermass mechanism for onescanning direction, which functions based on the law of conservation ofmomentum, is typically adopted (see, for example, U.S. patentapplication Ser. No. 09/260,544). The reaction force produced due todriving of the reticle stage can also be mechanically transferred to thebase, that is, the floor (the ground) by using a frame member (see, forexample, U.S. Pat. No. 5,874,820).

In conventional projection exposure apparatus, the reaction force of thestage to be transferred to the base is damped by a vibration-isolatingdevice, such as an anti-vibration table, so as to reduce vibration of aprojection optical system (projection lens) and vibration of the stagetransmitted via the base due to the reaction force. Although thereaction force is damped by being transferred to the base, a nontrivialamount of vibration, from the viewpoint of the level required undercurrent micro-fabrication requirements, is given to the projectionoptical system and to the stage. Such vibration resulting from thereaction force deteriorates exposure accuracy of a scanning stepper thatperforms an exposure operation while scanning a stage (and a wafer or areticle).

While transmission of reaction force can be substantially completelyprevented by absorbing the reaction force by the countermass mechanism,the conventional countermass mechanism employs a countermass that movesin a direction opposite from the driving direction of a stage by adistance proportional to the driving distance of the stage. For thisreason, the stroke of the countermass must be set in accordance with (inproportion to) the total stroke of the stage, which increases the sizeof the exposure apparatus.

In light of the above, one object of the present invention is to providea stage assembly that precisely positions a device. Another object is toprovide a stage assembly that minimizes the influence of the reactionforces of the stage mover assembly upon the position of the stage, thestage base, and the apparatus frame. Still another object is to providea stage assembly having an improved reaction mass assembly. Anotherobject is to provide an improved system and method for resetting theposition of a reaction mass assembly. Yet another object is to providean exposure apparatus capable of manufacturing precision devices such ashigh density, semiconductor wafers.

SUMMARY OF THE INVENTION

The invention has been made in view of the above circumstances, and itis one object of the invention to provide an exposure apparatus andmethod that allows precise exposure without increasing the size of theexposure apparatus.

The present invention is directed to a method and apparatus forresetting a reaction mass assembly of a stage assembly. The stageassembly is useful with an apparatus to sequentially position a devicefor one or more manufacturing operations performed by the apparatus. Thestage assembly includes a stage, a stage mover assembly, a reaction massassembly, a reaction mover assembly and a control system. The stageretains the device. The stage mover assembly moves the stage relative toa stage base. The reaction mass assembly reduces and minimizes theamount of reaction forces from the stage mover assembly that aretransferred to the stage base.

The reaction mover assembly moves the reaction mass assembly relative tothe stage base to reset the position of the reaction mass assembly. Morespecifically, the control system directs and controls current to thereaction mover assembly (i) to control the position of the reaction massassembly, (ii) to prevent the reaction mass assembly from achieving aconstant velocity, (iii) to correct external disturbances that caninfluence the position of the reaction mass assembly, and (iv) toprevent the center of gravity of the stage assembly from shifting.

Preferably, the control system controls current to the reaction moverassembly based upon the status of the one or more operations performedby the apparatus. This allows the control system to control and directcurrent to the reaction mover assembly in a way that minimizes thedisturbances created by the reaction mover assembly on the stageassembly and the apparatus. More specifically, the timing and/or theamount of current from the control system directed to the reaction moverassembly is varied to minimize the influence of the disturbances createdby the reaction mover assembly on the stage assembly. The timing and/oramount of current can also be varied according the type of operationsperformed by the apparatus.

In one embodiment of the present invention, the control system does notdirect current to the reaction mover assembly during at least one of theoperations performed by the apparatus and the control system directscurrent to the reaction mover assembly between the operations performedby the apparatus. In this embodiment, the control system controls anddirects current to the reaction mover assembly so that the reactionmover assembly only moves and corrects the position of the reaction massassembly at selected times or intervals.

For example, if the stage assembly is utilized for an exposureapparatus, the reaction mover assembly can be activated betweenexposures and deactivated during an exposure. Stated another way, forthe exposure apparatus, the control system can be designed to directcurrent to the reaction mover assembly when an illumination system is inan off position and not direct current when the illumination system isin an on position. In the on position, the illumination source directs abeam of light energy towards the stage assembly. In contrast, in the offposition, the illumination source does not direct a beam of light energytowards the stage assembly. Thus, the control system controls current tothe reaction mover assembly based upon the position of the illuminationsource.

In this embodiment, the control system can direct current to thereaction mover assembly (i) between the forming of each image on thedevice, e.g. each chip on a semiconductor wafer, (ii) between theforming of each row of images on the device, e.g. each row of chips onthe wafer, (iii) between every scan of the device, or (iv) between eachdevice or wafer processed by the exposure apparatus. Because thereaction mover assembly is not activated during an exposure, thedisturbances created by the reaction mover assembly do not significantlyinfluence the position of the stage assembly.

In another embodiment of the present invention, the control system candirect current to the reaction mover assembly so that the rate ofmovement by the reaction mover assembly is greater between eachoperation performed by the apparatus than during each operation. In thisembodiment, the control system controls and directs current to thereaction mover assembly so that the reaction mover assembly makes onlyrelatively small corrections to the position of the reaction massassembly at selected times or intervals and the reaction mover assemblymakes relatively large corrections to the position of the reaction massassembly between these selected times or intervals.

For an exposure apparatus, the control system can control and directcurrent to the reaction mover assembly at a different rate during anexposure than between exposures. For example, during an exposure, thecontrol system directs current to the reaction mover assembly so thatthe forces generated by the reaction mover assembly are relatively smalland the gain is low. Alternately, between exposures, the control systemdirects current to the reaction mover assembly so that the forcesgenerated by the reaction mover assembly are relatively large and thegain is high.

As provided herein, the control system can direct a relatively largecurrent to the reaction mover assembly (i) between the forming of eachimage on the device, e.g. each chip on a semiconductor wafer, (ii)between the forming of each row of images on the device, e.g. each rowof chips on the wafer, (iii) between every scan of the device, or (iv)between each device or wafer processed by the exposure apparatus. Withthis design, the reaction mover assembly makes relatively largeadjustments to the position of the reaction mass assembly when theillumination source is in the off position and makes relatively smalladjustments to the position of the reaction mass assembly when theillumination source is in the on position. Thus, the control systemdirects more current to the reaction mover assembly when theillumination source is in the off position than when the illuminationsource is in the on position.

Because the reaction mover assembly makes only sight movements during anexposure, the disturbances created by the reaction mover assembly do notsignificantly influence the position of the stage assembly.

The present invention is also directed to a method for making a stageassembly, a method for making an exposure apparatus, a method for makinga device and a method for manufacturing a wafer.

BRIEF DESCRIPTION OF THE DRAWINGS

The novel features of this invention, as well as the invention itself,both as to its structure and its operation, will be best understood fromthe accompanying drawings, taken in conjunction with the accompanyingdescription, in which similar reference characters refer to similarparts, and in which:

FIG. 1 is a perspective view of a first embodiment of a stage assemblyhaving features of the present invention;

FIG. 2 is a top plan view of the stage assembly of FIG. 1;

FIG. 3 is a front plan view of the stage assembly of FIG. 1;

FIG. 4 is a perspective view of a stage having features of the presentinvention;

FIG. 5A is a perspective view of a device table having features of thepresent invention;

FIG. 5B is a top plan view of the device table of FIG. 5A;

FIG. 6A illustrates a perspective view of a pair of electromagneticactuators having features of the present invention;

FIG. 6B illustrates an exploded perspective view of the actuators ofFIG. 6A;

FIG. 7A is a simplified, schematic top view of a portion of a stageassembly;

FIG. 7B is another, simplified schematic top view of a portion of thestage assembly;

FIG. 7C is a simplified block diagram that illustrates the operation ofa control system having features of the present invention;

FIG. 8 is a perspective view of a second embodiment of a stage assemblyhaving features of the present invention;

FIG. 9 is a top plan view of the stage assembly of FIG. 8;

FIG. 10 is an exploded perspective view of a reaction mass assemblyillustrated in FIG. 8;

FIG. 11 is a perspective view of a third embodiment of a stage assemblyhaving features of the present invention;

FIG. 12 is a perspective view of a reaction mass assembly illustrated inFIG. 11;

FIG. 13 is an exploded perspective view of the reaction mass assembly ofFIG. 11;

FIG. 14 is a perspective view of a fourth embodiment of a stage assemblyhaving features of the present invention;

FIG. 15 is a perspective view of a reaction mass assembly illustrated inFIG. 14;

FIG. 16 is an exploded perspective view of the reaction mass assembly ofFIG. 15;

FIG. 17A is a simplified schematic top view of a portion of a stageassembly;

FIG. 17B is a simplified block diagram that illustrates the operation ofa control system having features of the present invention;

FIG. 18 is a schematic illustration of an exposure apparatus havingfeatures of the present invention;

FIG. 19 is a flow chart that outlines a process for manufacturing adevice in accordance with the present invention; and

FIG. 20 is a flow chart that outlines device processing in more detail.

FIG. 21 is a schematic view showing the configuration of an exposureapparatus according to an embodiment of the invention;

FIG. 22 is a perspective view of a wafer stage assembly shown in FIG.21;

FIG. 23 is a partly broken view of a wafer stage and a wafer drivingdevice shown in FIG. 22;

FIG. 24A is a cross-sectional view, taken along line D—D in FIG. 22;

FIG. 24B is an explanatory view of an X-axis stationary member and aframe shown in FIG. 22, as viewed from the +X-axis direction;

FIG. 25 is a partly broken view of an X-axis moving member shown in FIG.23, in which the X-axis stationary member is omitted;

FIG. 26 is an explanatory view of an X restraint mechanism;

FIG. 27 is an explanatory view showing the positions of the centers ofgravity of the wafer stage and the wafer driver;

FIG. 28 is an explanatory view illustrating an exposure process for awafer;

FIG. 29 is a schematic structural view of an exposure apparatusaccording to a modification of the first embodiment; and

FIG. 30 is an explanatory view of a wafer stage assembly shown in FIG.29.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

Referring initially to FIG. 1, a stage assembly 10, having features ofthe present invention, includes a stage base 12, at least one stage 14(two are illustrated), a stage mover assembly 16, a reaction massassembly 18, a measurement system 20 (only a portion is illustrated inFIG. 1), and a control system 22. The stage assembly 10 is positionedabove a mounting base 24 (illustrated in FIG. 18). As an overview, thestage mover assembly 16 precisely moves each stage 14 relative to thestage base 12. Further, the reaction mass assembly 18 reduces andminimizes the amount of reaction forces from the stage mover assembly 16that are transferred to the stage base 12 and the mounting base 24.

The stage assembly 10 is particularly useful for precisely positioning adevice 26 during a manufacturing and/or an inspection process. The typeof device 26 positioned and moved by the stage assembly 10 can bevaried. For example, the device 26 can be a semiconductor wafer 28, andthe stage assembly 10 can be used as part of an exposure apparatus 30(illustrated in FIG. 18) for precisely positioning the semiconductorwafer 28 during manufacturing of the semiconductor wafer 28.Alternately, for example, the stage assembly 10 can be used to moveother types of devices during manufacturing and/or inspection, to move adevice under an electron microscope (not shown), or to move a deviceduring a precision measurement operation (not shown).

Some of the Figures provided herein include a coordinate system thatdesignates an X axis, a Y axis, and a Z axis. It should be understoodthat the coordinate system is merely for reference and can be varied.For example, the X axis can be switched with the Y axis and/or the stageassembly 10 can be rotated.

A number of alternate embodiments of the stage assembly 10 areillustrated in the Figures. In particular, FIG. 1 illustrates aperspective view of a first embodiment of the stage assembly 10, FIG. 8illustrates a perspective view of a second embodiment of the stageassembly 10, FIG. 11 illustrates a perspective view of a thirdembodiment of the stage assembly 10, and FIG. 14 illustrates aperspective view of a fourth embodiment of the stage assembly 10.

In each embodiment illustrated herein, each stage 14 is moved relativeto the stage base 12 along the X axis, along the Y axis, and about the Zaxis (collectively “the planar degrees of freedom”). More specifically,the stage mover assembly 16 moves and positions each stage 14 along theX axis, along the Y axis, and about the Z axis under the control of thecontrol system 22. Additionally, in each embodiment illustrated, thestage assembly 10 includes two stages 14 that independently moverelative to the stage base 12. Alternately, however, each stage assembly10 could include only one stage 14 or more than two stages 14.

Importantly, the reaction mass assembly 18 reduces and minimizes theamount of reaction force from the stage mover assembly 16 that aretransferred to the stage base 12 and the mounting base 24. As anoverview, in the embodiments provided herein, the reaction mass assembly18 includes an X reaction component 33A and a Y reaction component 33B.The X reaction component 33A moves relative to the stage base 12 with atleast two degrees of freedom and more preferably, three degrees offreedom. The Y reaction component 33B moves relative to the stage base12 with at least one degree of freedom and more preferably three degreesof freedom.

Further, in the embodiments provided herein, the X reaction component33A is coupled to the Y reaction component 33B and moves relative to theY reaction component 33B along the X axis. Additionally, the X reactioncomponent 33A and the Y reaction component 33B move concurrently alongthe Y axis relative to the stage base 12. In some of the embodiments,the X reaction component 33A and the Y reaction component 33B also moveconcurrently along the X axis and about the Z axis relative to the stagebase 12.

In a preferred embodiment of the present invention, the reaction massassembly 18 is free to move along the X axis, along the Y axis, andabout the Z axis relative to the stage base 12. In this embodiment, whenthe stage mover assembly 16 applies a force to the stage 14 along the Xaxis, the Y axis, and/or about the Z axis, an equal and opposite forceis applied to the reaction mass assembly 18. Further, the control system22 corrects the position of the reaction mass assembly 18 along the Xaxis, along the Y axis, and about the Z axis.

The reaction mass assembly 18 provided herein, minimizes the disturbancethat is transferred to the stage base 12. This improves the positioningperformance of the stage assembly 10. Further, for an exposure apparatus30, this allows for more accurate positioning of the semiconductor wafer28 relative to a reticle 32 (illustrated in FIG. 18).

The stage base 12 supports a portion of the stage assembly 10 above themounting base 24. The design of the stage base 12 can be varied to suitthe design requirements of the stage assembly 10. In the embodimentillustrated in FIGS. 1-3, the stage base 12 is generally rectangularshaped and includes a planar base top 34 (sometimes referred to as aguide face), an opposed planar base bottom 36, four base sides 38, and aplurality of spaced apart base fluid pads 40 (illustrated in FIG. 3).The base fluid pads 40 are secured to base top 34.

In this embodiment, the reaction mass assembly 18 is maintained abovethe stage base 12 with a vacuum type fluid bearing. More specifically,in this embodiment, each of the base fluid pads 40 includes a pluralityof spaced apart fluid outlets (not shown), and a plurality of spacedapart fluid inlets (not shown). Pressurized fluid (not shown) isreleased from the fluid outlets towards a reaction base 42 of the Yreaction component 33B of the reaction mass assembly 18. A vacuum ispulled in the fluid inlets to create a vacuum preload type, fluidbearing between the base top 34 and the reaction base 42. The vacuumpreload type fluid bearing maintains the reaction mass assembly 18,spaced apart along the Z axis, relative to the stage base 12. Further,the vacuum preload type fluid bearing allows for motion of the Xreaction component 33A, and the Y reaction component 33B along the Xaxis, along the Y axis, and about the Z axis relative to the stage base12.

Alternately, the reaction mass assembly 18 can be supported spaced apartfrom the stage base 12 in other ways. For example, a magnetic typebearing or a ball bearing type of assembly could be utilized that allowsfor motion of the reaction mass assembly 18 relative to the stage base12.

Preferably, referring to FIG. 18, the stage base 12 is secured withresilient base isolators 44 and an apparatus frame 46 to the mountingbase 24. The base isolators 44 reduce the effect of vibration of theapparatus frame 46 causing vibration on the stage base 12. Typically,three or four spaced apart base isolators 44 are utilized. Each baseisolator 44 can include a pneumatic cylinder (not shown) and an actuator(not shown). Suitable base isolators 44 are sold by TechnicalManufacturing Corporation, located in Peabody, Mass., or NewportCorporation located in Irvine, Calif.

The stage 14 retains the device 26. The stage 14 is precisely moved bythe stage mover assembly 16 to precisely position the device 26. Thedesign of each stage 14 can be varied to suit the design requirements ofthe stage assembly 10. A perspective view of one of the stages 14 isprovided in FIG. 4. In this embodiment, the stage 14 includes a devicetable 48, a guide assembly 50, a portion of the stage mover assembly 16,and a portion of the measurement system 20. The design of each stage 14illustrated in FIGS. 1-3 is substantially the same as the stage 14illustrated in FIG. 4. Accordingly, the present discussion describesonly one of the stages 14.

The design and movement of the device table 48 for each stage 14 can bevaried to suit the design requirements of the stage assembly 10. In theembodiment illustrated in FIGS. 1-4, the device table 48 moves relativeto the guide assembly 50 along the Y axis. Further, the device table 48includes: (i) an upper table component 52, (ii) a lower table component54 positioned below the upper table component 52, (iii) a pair of spacedapart table fluid pads 56 (only one is illustrated in FIG. 4) positionedbelow the lower table component 54.

The upper table component 52 is generally rectangular shaped andincludes a table top 58, a table bottom 60, four table sides 62 (onlytwo sides are illustrated in the Figures), and a device holder 63(illustrated in FIGS. 5A and 5B). The device holder 63 is positionednear the table top 58 and retains the device 26 during movement of thestage 14. The device holder 63 can be a vacuum chuck, an electrostaticchuck, or some other type of clamp.

The lower table component 54 includes a generally rectangular tubeshaped outer guide section 64, and generally rectangular tube shapedinner guide section 65. The outer guide section 64 is positioned belowthe upper table component 52. The outer guide section 64 defines agenerally rectangular shaped guide channel 66 that is sized and shapedto receive a portion of the guide assembly 50. The guide channel 66defines a pair of spaced apart side guide surfaces 68. The outer guidesection 64 also includes a plurality of section apertures 70 that extendtransversely through the outer guide section 64 to reduce the weight ofthe outer guide section 64.

Additionally, the outer guide section 64 includes a pair of spacedapart, section fluid pads 72 (only one is illustrated in the Figures)that are positioned along the side guide surfaces 68 in the guidechannel 66. In this embodiment, each section fluid pad 72 includes aplurality of spaced apart fluid outlets (not shown). Pressurized fluid(not shown) is released from the fluid outlets towards the guideassembly 50 to create a fluid bearing between the device table 48 andthe guide assembly 50. The fluid bearing maintains the device table 48spaced apart from the guide assembly 50 along the X axis and allows formotion of the device table 48 along the Y axis relative to the guideassembly 50.

The inner guide section 65 is positioned within the guide channel 66,below the upper table component 52. The inner guide section 65 defines agenerally rectangular shaped opening 74 that is sized and shaped toreceive a portion of the guide assembly 50. Stated another way, theinner guide section 65 encircles a portion of the guide assembly 50. Inthe embodiments provided herein, the inner guide section 65 supports aportion of the stage mover assembly 16 as provided below.

The table fluid pads 56 extend downwardly from the lower table component54. Each table fluid pad 56 includes a plurality of spaced apart fluidoutlets (not shown), and a plurality of spaced apart fluid inlets (notshown). Pressurized fluid (not shown) is released from the fluid outletstowards the reaction base 42 of the reaction mass assembly 18. A vacuumis pulled in the fluid inlets to create a vacuum preload type fluidbearing between the table fluid pads 56 and the reaction base 42. Thevacuum preload type fluid bearing maintains the device table 48 spacedapart along the Z axis relative to the reaction base 42. Further, thevacuum preload type fluid bearing allows for motion of the device table48 along the X axis, along the Y axis, and about the Z axis relative tothe reaction base 42.

Alternately, the device table 48 can be supported above the reactionbase 42 in other ways. For example, a magnetic type bearing or a ballbearing type of assembly could be utilized that allows for movement ofthe device table 48 relative to the reaction base 42.

FIGS. 5A and 5B illustrate an alternate embodiment of a device table 48having features of the present invention. In this design, the devicetable 48 includes a table mover assembly 75. Further, in this design,the upper table component 52 is moveable relative to the lower tablecomponent 54. More specifically, the table mover assembly 75 adjusts theposition of the upper table component 52 relative to the lower tablecomponent 54 of the device table 48.

The design of the table mover assembly 75 can be varied to suit thedesign requirements to the stage assembly 10. In the embodimentillustrated in FIGS. 5A and 5B, the table mover assembly 75 adjusts theposition of the upper table component 52 and the device holder 63relative to the lower table component 54 with six degrees of freedom.Alternately, for example, the table mover assembly 75 can be designed tomove the upper table component 52 relative to the lower table component54 with only three degrees of freedom. The table mover assembly 75 caninclude one or more rotary motors, voice coil motors, linear motors,electromagnetic actuators 79, or some other force actuators.

In the embodiment illustrated in FIGS. 5A and 5B, the table moverassembly 75 includes three spaced apart, horizontal table movers 76 andthree spaced apart, vertical table movers 78. The horizontal tablemovers 76 move the upper table component 52 along the X axis, along theY axis, and about the Z axis relative to the lower table component 54.The vertical table movers 78 move the upper table component 52 about theX axis, about the Y axis, and along the Z axis relative to the lowertable component 54.

The design of each table mover 76, 78 can be varied. In the embodimentillustrated in the Figures, each of the horizontal table movers 76includes a pair of electromagnetic actuators 79, and each of thevertical table movers 78 is a non-commutated actuator commonly referredto as a voice coil actuator.

FIGS. 6A and 6B illustrate a perspective view of a preferred pair ofelectromagnetic actuators 79. More specifically, FIG. 6A illustrates aperspective view of a pair of electromagnetic actuators 79 commonlyreferred to as an E/I core actuators 214, and FIG. 6B illustrates anexploded perspective view of the E/I core actuators 214. Each E/I coreactuator 214 is essentially an electromagnetic attractive device. EachE/I core actuator 214 includes an E shaped core 80, a tubular conductor81, and an I shaped core 82. The E core 80 and the I core 82 are eachmade of a magnetic material such as iron, silicon steel, or Ni—Fe steel.The conductor 81 is positioned around the center bar of the E core 80.The combination of the E core 80 and the conductor 81 is sometimesreferred to herein as an electromagnet. Further, the I core 82 issometimes referred to herein as a target.

Each electromagnet and target is separated by an air gap g (which isvery small and therefore difficult to see in the figures). Theelectromagnets are variable reluctance actuating portions and thereluctance varies with the distance defined by the gap g, which, ofcourse also varies the flux and force applied to the target. Theattractive force between the electromagnet and the target is defined by:F=K(i/g)²

Where F is the attractive force, measured in Newtons;

K=an electromagnetic constant which is dependent upon the geometries ofthe E-shaped electromagnet, I-shaped target, and number of conductorturns about the magnet. K=1/2N² μ_(o)wd; where N=the number of turnsabout the E-shaped magnet conductor 81; μ_(o)=a physical constant ofabout 1.26×10⁻⁶H/m; w=the half width of the center of the E-shaped core80 in meters; and d=the depth of the center of the E-shaped core 80 inmeters. In a preferred embodiment, K=7.73×10⁻⁶ kg m³/s²A²;

i=current, measured in amperes; and

g=the gap distance, measured in meters.

Current (not shown) directed through the conductor 81 creates anelectromagnetic field that attracts the I core 82 towards the E core 80.The amount of current determines the amount of attraction. Statedanother way, when the conductor of an electromagnet is energized, theelectromagnet generates a flux that produces an attractive force on thetarget in accordance with the formula given above, thereby functioningas a linear actuating portion. Because the electromagnets can onlyattract the targets, they must be assembled in pairs that can pull inopposition. The targets are fixed to the upper table component 52 andmove relative to the lower table component 54. Opposing pairs ofelectromagnets are secured to the lower table component 54 on oppositesides of the targets. By making a current through the one conductor 81of the pair of electromagnets larger than the current through the otherconductor 81 in the pair, a differential force can be produced thatdraws the target in one direction or its opposing direction.

Preferably, the targets are attached to the upper table component 52 insuch a way that the pulling forces of the opposing pair ofelectromagnets do not distort the upper table component 52. This ispreferably accomplished by mounting the targets for an opposing pair ofelectromagnets very close to one another, preferably peripherally of theupper table component 52. It is preferable to extend a thin web 83 ofmaterial (FIG. 5B) that is made of the same material as the upper tablecomponent 52. The opposing electromagnets are mounted on the lower tablecomponent 54 by a predetermined distance, when thin web 83 and targetsare positioned there between, a predetermined gap g is formed betweeneach set of electromagnet and target. With this arrangement, only theresultant force, derived from the sum of the forces produced by the pairof electromagnets and targets, is applied to the upper table component52 via transfer of the force through thin web 83. In this way, opposingforces are not applied to opposite sides of the upper table component 52and stage distortion problems resulting from that type of arrangementare avoided.

FIG. 5B illustrates a preferred arrangement of the horizontal tablemovers 76. In this design, one opposing pair of attraction onlyactuators 79 are mounted so that the attractive forces produced therebyare substantially parallel with the X axis. Two opposing pairs ofattraction only actuators 79 are mounted so that attractive forces fromeach pair are produced substantially parallel with the Y axis. With thisarrangement, the horizontal table movers 76 can make fine adjustments tothe position of the upper table component 52 relative to the lower tablecomponent 54 along the X axis, along the Y axis, and about the Z axis.More specifically, actuation of the single pair of electromagneticactuators 79 aligned along the X axis can achieve fine movements alongthe X axis. Actuation of the two pairs of electromagnetic actuators 79aligned along the Y axis can control fine movements of the upper stagecomponent 52 along the Y axis or in rotation (clockwise orcounterclockwise) in the X-Y plane (i.e., Theta Z control). Y axismovements are accomplished by resultant forces from both pairs that aresubstantially equal and in the same direction. Theta Z movements aregenerally accomplished by producing opposite directional forces from thetwo pairs of electromagnets, although unequal forces in the samedirection will also cause some Theta Z adjustment.

Alternately, for example, two opposing pairs of electromagneticactuators 79 can be mounted parallel with the Y direction, and oneopposing pair of electromagnetic actuators 79 could be mounted parallelwith the X direction. Other arrangements are also possible, but thepreferred arrangement minimizes the number of actuatingportions/bearings required for the necessary degrees of control.

Preferably, the lines of force of the electromagnetic actuators 79 arearranged to act through the center of gravity of the upper tablecomponent 52. The two Y pairs of electromagnetic actuators 79 arepreferably equidistant from the center of gravity of the upper tablecomponent 52.

The vertical table movers 78 are used to precisely position the uppertable component 52 relative to the lower table component 54 along the Zaxis, about the X axis, and about the Y axis (collectively referred toas “vertical degrees of freedom”). Because control in the three verticaldegrees of freedom requires less dynamic performance (e.g., accelerationrequirements are relatively low), and is easier to accomplish, lowerforce requirements exist than in the previously described X, Y, andTheta Z degrees of freedom. Accordingly, three voice coil motors can beused as the vertical table movers 78 to adjust the position of the uppertable component 52 in the vertical degrees of freedom. In this design,each motor includes a magnet array 78A attached to the lower tablecomponent 54 and a conductor array 78B attached to the upper tablecomponent 52.

Preferably, fluid bellows 85 (illustrated in phantom) are utilized tosupport the dead weight of the upper table component 52. The fluidbellows 85 prevent overheating of the vertical table movers 78. Asprovided herein, one fluid bellow 85 is preferably positioned next tovertical table mover 78. The bellows 85 have very low stiffness in alldegrees of freedom so they do not significantly interfere with thecontrol of the upper table component 52.

The guide assembly 50 for each stage 14 is used to move the device table48 along the X axis and about the Z axis and guide the movement of thedevice table 48 along the Y axis. The design of the guide assembly 50can be varied to suit the design requirements of the stage assembly 10.In the embodiment illustrated in FIGS. 1-4, the guide assembly 50includes an upper beam 84, a lower guide 86, a first guide end 88, and aspaced apart second guide end 90.

The upper beam 84 and the lower guide 86 are spaced apart, substantiallyparallel, and extend between the guide ends 88, 90.

The upper beam 84 is somewhat rectangular shaped and defines a portionof the stage mover assembly 16. The upper beam 84 fits within theopening 74 of the inner guide section 65. The lower guide 86 is somewhatrectangular shaped and includes a plurality of apertures 92 to reducethe mass. The lower guide 86 also includes a pair of opposed sides 94(only one side is illustrated in the Figures).

Pressurized fluid (not shown) is released from the fluid outlets of thesection fluid pads 72 towards the opposed sides 94 of the lower guide 86to create a fluid bearing between the device table 48 and the guideassembly 50. The fluid bearing maintains the device table 48 spacedapart from the guide assembly 50 along the X axis and allows for motionof the device table 48 along the Y axis relative to the guide assembly50.

The guide ends 88, 90 secure the upper beam 84 to the lower guide 86,and secure a portion of the stage mover assembly 16 to the guideassembly 50. Additionally, each of the guide ends 88, 90 includes aguide fluid pad 96 that is positioned adjacent to the reaction base 42.In this embodiment, each of the guide fluid pads 96 includes a pluralityof spaced apart fluid outlets (not shown), and a plurality of spacedapart fluid inlets (not shown). Pressurized fluid (not shown) isreleased from the fluid outlets towards the reaction base 42 and avacuum is pulled in the fluid inlets to create a vacuum preload type,fluid bearing between each of the guide fluid pads 96 and the reactionbase 42. The vacuum preload type, fluid bearing maintains the guideassembly 50 spaced apart along the Z axis relative to the reaction base42 and allows for motion of the guide assembly 50 along the X axis,along the Y axis, and about the Z axis relative to 30 the reaction base42.

Alternately, the guide assembly 50 can be supported spaced apart fromthe reaction base 42 by other ways. For example, a magnetic type bearingor a ball bearing type of assembly could be utilized that allows formotion of the guide assembly 50 relative to the reaction base 42.

The components of each stage 14 can be made of a number of materialsincluding ceramic, such as alumina or silicon carbide; metals such asaluminum; composite materials; or plastic.

The stage mover assembly 16 controls and moves each stage 14 relative tothe stage base 12. The design of the stage mover assembly 16 and themovement of the stages 14 can be varied to suit the movementrequirements of the stage assembly 10. In the embodiment illustrated inFIGS. 1-3, the stage mover assembly 16 moves the stage 14 with arelatively large displacement along the X axis, a relatively largedisplacement along the Y axis, and a limited 10 displacement about the Zaxis (theta Z) relative to the stage base 12. In this embodiment, thestage mover assembly 16 includes: (i) a first X stage mover 98, (ii) asecond X stage mover 100, (iii) an upper Y guide mover 102, (iv) a lowerY guide mover 104, and (v) a Y stage mover 106. The X stage movers 98,100 move the stage 14 along the X axis and about the Z axis. The Y stagemovers 102, 104, 106 move the guide assembly 50 and the stage 14 alongthe Y axis. More specifically, in this embodiment, (i) the X stagemovers 98, 100 move the guide assembly 50 with a relatively largedisplacement along the X axis and with a limited range of motion aboutthe Z axis (theta Z), (ii) the Y guide movers 102, 104 move the guideassembly 50 with a small displacement along the Y axis, and (iii) the Ystage mover 106 moves the device table 48 with a relatively largedisplacement along the Y axis.

The design of each mover 98, 100, 102, 104, 106 can be varied to suitthe movement requirements of the stage assembly 10. As provided herein,each mover 98, 100, 102, 104, 106 includes a first component 108 and anadjacent second component 110, which interact with the first component108. In the embodiments provided herein, each of the Y guide movers 102,104 is an E/I core type actuator. Further, in the embodiments providedherein, for the X stage movers 98, 100 and the Y stage mover 106, one ofthe components 108, 110 includes one or more magnet arrays (not shown)and the other component 108, 110 includes one or more conductor arrays(not shown).

Each magnet array includes one or more magnets (not shown). The designof each magnet array and the number of magnets in each magnet array canbe varied to suit the design requirements of the movers 98, 100, 106.Each magnet can be made of a permanent magnetic material such as NdFeB.

Each conductor array includes one or more conductors (not shown). Thedesign of each conductor array and the number of conductors in eachconductor array is varied to suit the design requirements of the movers98, 100, 106. Each conductor can be made of metal such as copper or anysubstance or material responsive to electrical current and capable ofcreating a magnetic field such as superconductors.

Electrical current (not shown) is individually supplied to eachconductor in each conductor array by the control system 22. For eachmover 98, 100, 106, the electrical current in each conductor interactswith a magnetic field (not shown) generated by one or more of themagnets in the magnet array. This causes a force (Lorentz force) betweenthe conductors and the magnets that can be used to move the stage 14relative to the stage base 12.

Specifically, the first component 108 and the second component 110 ofeach X stage mover 98, 100 interact to selectively move the stage 14along the X axis and about the Z axis relative to the stage base 12. Inthe embodiment illustrated in the FIG. 1, each X stage mover 98, 100 isa commutated, linear motor.

The first component 108 for the first X stage mover 98 is secured to afirst X reaction mass 112 of the X reaction component 33A of thereaction mass assembly 18 while the second component 110 of the first Xstage mover 98 is secured to the first guide end 88 of the guideassembly 50. Similarly, the first component 108 for the second X stagemover 100 is secured to a second X reaction mass 114 of the X reactioncomponent 33A of the reaction mass assembly 18 while the secondcomponent 110 of the second X stage mover 100 is secured to the secondguide end 90 of the guide assembly 50. In this embodiment, the firstcomponent 108 of each X stage mover 98, 100 includes a conductor array(not shown) while the second component 110 of each X stage mover 98, 100includes a pair of spaced apart magnet arrays (not shown). Alternately,for example, the first component 108 of each X stage mover 98, 100 caninclude a magnet array (not shown) while the second component 110 ofeach X stage mover 98, 100 can include a pair of spaced apart conductorarrays (not shown).

It should be noted that the first X stage mover 98 for each of thestages 14 illustrated in the FIGS. 1-3 share the same first component108. Similarly, the second X stage mover 100 for each of the two stages14 illustrated in the FIGS. 1-3 share the same first component 108.

With the design provided herein, the X stage movers 98, 100 makerelatively large displacement adjustments to the position of the guideassembly 50 along the X axis. The required stroke of the X stage movers98, 100 along the X axis will vary according to desired use of the stageassembly 10. More specifically, for an exposure apparatus 30, generally,the stroke of the X stage movers 98, 100 for moving the semiconductorwafer 28 is between approximately two hundred (200) millimeters and onethousand (1000) millimeters.

The X stage movers 98, 100 also make relatively slight adjustments toposition of each stage 14 about the Z axis. In order to make theadjustments about the Z axis, the second component 110 of one of the Xstage movers 98, 100 is moved relative to the second component 110 ofthe other X stage mover 98, 100. With this design, the X stage movers98, 100 generate torque about the Z axis. A gap (not shown) existsbetween the first component 108 and the second component 110 of each Xstage mover 98, 100 to allow for slight movement of each stage 14 aboutthe Z axis. Typically, the gap is between approximately one millimeterand five millimeters. However, depending upon the design of theparticular mover, a larger or smaller gap may be utilized.

The Y guide movers 102, 104 selectively move the guide assembly 50 alongthe Y axis relative to the stage base 12. In the embodiment illustratedin FIGS. 1-3, each Y guide mover 102, 104 includes an opposed pair ofelectromagnetic actuators. The electromagnetic actuators consume lesspower and generate less heat than a voice coil motor or a linear motor.Suitable 25 electromagnetic actuators include the E/I core actuators 214described above and illustrated in FIGS. 6A and 6B.

In the embodiments provided herein: (i) the combination E shaped coreand conductor of each electromagnetic actuator is considered the secondcomponent 110 of each Y guide mover 102, 104 and is secured to the guideassembly 50, and (ii) the I shaped core of each electromagnetic actuatoris considered the first component 108 of each Y guide mover 102, 104 andis secured to the second X reaction mass 114 of the reaction massassembly 18. In this embodiment, each Y guide mover 102, 104 includestwo E core and conductor combinations that are separated by a row of Icores.

It should be noted that the upper Y guide mover 102 for each of thestages 14 illustrated in the FIGS. 1-3 share the same first component108. Similarly, the lower Y guide mover 104 for each of the two stages14 illustrated in the FIGS. 1-3 share the same first component 108.

The Y stage mover 106 moves the stage 14 with a relatively largedisplacement along the Y axis relative to the stage base 12. Morespecifically, the first component 108 and the second component 110 ofthe Y stage mover 106 interact to selectively move the device table 48along the Y axis relative to the guide assembly 50. In the embodimentillustrated in the FIGS. 1-3, the Y stage mover 106 is a commutated,linear motor. The first component 108 for the Y stage mover 106 issecured to the upper beam 84 of the guide assembly 50, and the secondcomponent (not shown) is secured to the inner guide section 65 of thedevice table 48. In this embodiment, the first component 108 of the Ystage mover 106 includes a conductor array (not shown) and the secondcomponent 110 of the Y stage mover 106 includes a magnet array (notshown). Alternately, for example, the first component 108 of the Y stagemover 106 could include a magnet array (not shown) while the secondcomponent 110 of the Y stage mover 106 could include a conductor array(not shown).

With this design, the Y stage mover 106 makes relatively largedisplacement adjustments to the position of the device table 48 alongthe Y axis. The required stroke of the Y stage mover 106 along the Yaxis will vary according to desired use of the stage assembly 10. Morespecifically, for an exposure apparatus 30, generally, the stroke of theY stage mover 106 for moving the semiconductor wafer 28 is betweenapproximately one hundred (100) millimeters and six hundred (600)millimeters.

The reaction mass assembly 18 reduces and minimizes the amount ofreaction forces from the stage movers 98, 100, 102, 104, 106 that istransferred to the stage base 12 and to the mounting base 24. Uniquely,the reaction mass assembly 18 provided herein is free to move with atleast two, and more preferably three, degrees of freedom. Morespecifically, the reaction mass assembly 18 is free to move along the Xaxis, along the Y axis, and about the Z axis relative to the stage base12. This design allows the reaction mass assembly 18 to reduce andminimize the amount of reaction forces from the stage movers 98, 100,102, 104, 106 that is transferred to the stage base 12 and to themounting base 24. Further, the reaction mass assembly 18 provided hereinreduces and minimizes the reaction forces for multiple stages 14.

The design of the reaction mass assembly 18 can be varied to suit thedesign requirements of the stage assembly 10. In the embodimentillustrated in FIGS. 1-3, the reaction mass assembly 18 includes the Yreaction component 33B, the X reaction component 33A, and a reactionmover assembly 124. In this design, the Y reaction component 33Bincludes the reaction base 42, and the X reaction component 33A includesthe first X reaction mass 112, and the second X reaction mass 114.Further, the reaction mass assembly 18 is supported above the stage base12 by the fluid bearings as provided above.

As an overview, through the principle of conservation of momentum,movement of each stage 14 with the X stage movers 98, 100 along the Xaxis in one direction, moves the X reaction masses 112, 114 of thereaction mass assembly 18 in the opposite direction along the X axis.Somewhat similarly, movement of each stage 14 with the Y stage movers102, 104, 106 along the Y axis in one direction, moves the X reactionmasses 112, 114 and the reaction base 42 along the Y axis in theopposite direction. With this design, the reaction forces from the stagemover assembly 16 are negated. This inhibits the reaction forces fromthe stage mover assembly 16 from influencing the position of the stagebase 12.

The reaction base 42 supports each stage 14 and the X reaction masses112, 114. The design of the reaction base 42 can be varied to suit thedesign requirements of the stage assembly 10. In the embodimentillustrated in FIGS. 1-3, the reaction base 42 is generally rectangularshaped and includes a planar, upper surface 126, a planar bottom surface128, and four sides 130.

The reaction base 42 also includes a mass guide assembly 131 that guidesthe X reaction masses 112, 114, and allow the X reaction masses 112, 114to move relative to the reaction base 42 along the X axis. In theembodiments provided herein, the reaction base 42 includes a pair ofbase guides 132. Each base guide 132 is a rectangular shaped channel inthe upper surface 126 that extends along the X axis. Pressurized fluidis released into the channel and a vacuum is created between thereaction base 42 and each of the X reaction masses 112, 114 to create avacuum preload type fluid bearing (not shown). The fluid bearingmaintains the X reaction masses 112, 114 spaced apart from the reactionbase 42, and allows for independent motion of the X reaction masses 112,114 along the X axis relative to the reaction base 42. Alternately, theX reaction masses 112, 114 can be supported above the reaction base 42by other ways such as magnetic type bearing (not shown) or a ballbearing type of 5 assembly (not shown).

It should be noted in this embodiment, that the X reaction masses 112,114 and the reaction base 42 move concurrently along the Y axis andabout the Z axis. Stated another way, the X reaction masses 112, 114 arerigidly coupled along the Y axis.

Referring to FIGS. 1-3, each of the X reaction masses 112, 114 includesa mass top 134, a mass bottom 136, a mass outer side 138, and a massinner side 140. Each of the X reaction masses 112, 114 also includes amass follower 142 that interacts with one the base guides 132 in thereaction base 42 to allow for movement of each X reaction mass 112, 114along the X axis. In the embodiment illustrated in FIGS. 1-3, the massfollower 142 is a rectangular shaped body that extends downward from themass bottom 136 of each X reaction mass 112, 114.

The first X reaction mass 112 is generally rectangular shaped andincludes a somewhat rectangular shaped first channel 144 that extendsinto the mass inner side 140 of the first X reaction mass 112. In thisembodiment, the first component 108 of the first X stage mover 98 ispositioned within the first channel 144 and secured to the first Xreaction mass 112.

The second X reaction mass 114 is somewhat rectangular shaped andincludes a rectangular shaped upper groove 146 in the mass top 134 and asomewhat rectangular shaped second channel 148 that extends into themass inner side 140 of the second X reaction mass 114. In thisembodiment, the first component 108 of the upper Y guide mover 102 ispositioned within the upper groove 146 and is secured to the second Xreaction mass 114. Additionally, the first component 108 of the second Xstage mover 100 and the first component (not shown) of the lower Y guidemover 104 are positioned within the second channel 148 and are securedto the second X reaction mass 114.

Additionally, each of the X reaction masses 112, 114 includes an “L”shaped bracket 150 that is secured to the mass outer side 138. Eachbracket 150 is used to secure a portion of the reaction mover assembly124 to the X reaction masses 112, 114.

The reaction mover assembly 124 makes minor corrections (i) to theposition of the X reaction masses 112, 114 relative to the reaction base42 and (ii) to the position of the reaction mass assembly 18 relative tothe stage base 12. As provided herein, the reaction mover assembly 124can adjust the position of the reaction mass assembly 18 relative to thestage base 12 in one degree of freedom, and more preferably, in threedegrees of freedom. For example, the reaction mover assembly 124 can:(i) move the X reaction component 33A relative to the Y reactioncomponent 33B along the X axis, (ii) move the X reaction component 33Aand the Y reaction component 33B concurrently relative to the stage base12 along the Y axis, (iii) move the X reaction component 33A and the Yreaction component 33B concurrently relative to the stage base 12 alongthe X axis, and/or (iv) move the X reaction component 33A and the Yreaction component 33B concurrently relative to the stage base 12 aboutthe Z axis.

In the embodiment illustrated in FIGS. 1-3, the reaction mover assembly124 is used to make minor corrections along the X axis, along the Yaxis, and about the Z axis to the position of the reaction mass assembly18 relative to the stage base 12. Further, the reaction mover assembly124 is used to 20 independently correct the position of the X reactionmasses 112, 114 along the X axis relative to the reaction base 42.

The design of the reaction mover assembly 124 can be varied according tothe design requirements of the stage assembly 10. For example, thereaction mover assembly 124 can include one or more rotary motors, voicecoil motors, 25 linear motors, electromagnetic actuators, and/or forceactuators. In the embodiment illustrated in the FIGS. 1-3, the reactionmover assembly 124 includes a first upper X reaction mover 152A, asecond upper X reaction mover 152B, a pair of lower X reaction movers154, and a Y reaction mover 156. Alternately, for example, the reactionmover assembly 124 could include a single, 30 lower X reaction mover anda pair of Y reaction movers.

In the embodiments illustrated in FIGS. 1-3, each reaction mover 152,154, 156 includes a first component 158, and an adjacent secondcomponent 160. In the embodiments provided herein, one of the components158, 160 of each mover 152, 154, 156 includes one or more magnet arrays(not shown) and the other component 158, 160 of each mover 152, 154, 156includes one or more conductor arrays (not shown). Electrical current(not shown) is individually supplied to each conductor array by thecontrol system 22. For each reaction mover 152, 154, 156, the electricalcurrent in each conductor interacts with a magnetic field (not shown)generated by one or more of the magnets in the magnet array. This causesa force (Lorentz force) between the conductors and the magnets.

Specifically, the first component 158 and the second component 160 ofeach upper X reaction mover 152 interact to selectively andindependently move one of the X reaction masses 112, 114 along the Xaxis relative to the reaction base 42. In the embodiment illustrated inthe FIG. 1, each upper X reaction mover 152 is a commutated, linearmotor. For the first upper X reaction mover 152A, the first component158 is secured to the first X reaction mass 112, while the secondcomponent 160 is secured to the reaction base 42. Similarly, for thesecond upper X reaction mover 1528, the first component 158 is securedto the second X reaction mass 114, while the second component 160 issecured to the reaction base 42.

In this embodiment, the first component 158 of each upper X reactionmover 152 includes a conductor array (not shown), while the secondcomponent 160 of each upper X reaction mover 152 includes a pair ofspaced apart magnet arrays (not shown). With this design, the upper Xreaction movers 152 can independently make corrections to the positionsof the X reaction masses 112, 114 along the X axis relative to thereaction base 42. Alternately, for example, the first component of eachupper X reaction mover 152 could include a pair of spaced apart magnetarrays while the second component of each upper X reaction mover 152could include a conductor array.

Preferably, the upper X reaction movers 152 include a measurement device(not shown) such as an encoder that provides information regarding theposition of the X reaction masses 112, 114 relative to the reaction base42 along 30 the X axis.

Somewhat similarly, the first component 158 and the second component 160of each lower X reaction mover 154 interact to collectively move thereaction base 42 along the X axis relative to the stage base 12, and torotate the reaction base 42 and the X reaction masses 112, 114 about theZ axis relative to the stage base 12. In the embodiment illustrated inthe FIG. 1, each lower X reaction mover 154 is a commutated, linearmotor. For each of the lower X reaction movers 154, the first component158 is secured to the reaction base 42 while the second component 160 issecured to the mounting base 24 with a ground frame 164 (illustrated inFIG. 18). Alternately, for example, the second component 160 of eachlower X reaction mover 154 can be secured to the stage base 12.

In this embodiment, the first component 158 of each lower X reactionmover 154 includes a conductor array (not shown), while the secondcomponent 160 of each lower X reaction mover 154 includes a pair ofspaced apart magnet arrays (not shown). With this design, the lower Xreaction movers 154 can make minor corrections to the positions of thereaction base 42 along the X axis relative to the stage base 12, and torotate the reaction base 42 and the X reaction masses 112, 114 about theZ axis relative to the stage base 12. Alternately, for example, thefirst component 158 of each lower X reaction mover 154 could include apair of spaced apart magnet arrays while the second component 160 ofeach upper X reaction mover 154 could include a conductor array.

Preferably, the lower X reaction movers 154 include a measurement device(not shown) such as an encoder that provides information regarding theposition of the reaction base 42 relative to the stage base 12 along theX axis and 20 about the Z axis.

Similarly, the first component 158 and the second component 160 of the Yreaction mover 156 interact to selectively move the reaction base 42 andthe X reaction masses 112, 114 concurrently along the Y axis relative tothe stage base 12. In the embodiment illustrated in FIG. 1, the Yreaction mover 156 is a commutated, linear motor. For the Y reactionmover 156, the first component 158 is secured to the reaction base 42while the second component 160 is secured to the mounting base 24 withthe ground frame 164 (illustrated in FIG. 18). Alternately, for example,the second component 160 of each Y reaction mover 156 can be secured tothe stage base 12.

In this embodiment, the first component 158 of each Y reaction mover 156includes a conductor array while the second component 160 of each Yreaction mover 156 includes a pair of spaced apart magnet arrays (notshown). With this design, the Y reaction movers 156 can make minorcorrections to the position of the reaction base 42 and the X reactionmasses 112, 114 along the Y axis relative to the stage base 12.Alternately, for example, the first component of the Y reaction mover156 could include a pair of spaced apart magnet arrays while the secondcomponent of the Y reaction mover 156 could include a conductor array.

Preferably, the Y reaction mover 156 includes a measurement device (notshown) such as an encoder that provides information regarding theposition of the reaction base 42 relative to the stage base 12 along theY axis.

For each of the embodiments provided herein, the ratio of the mass ofthe reaction mass assembly 18 to the mass stage 14 is preferablyrelatively high. This will minimize the movement of the reaction massassembly 18 and minimize the required travel of the reaction movers 152,154, 156. A suitable ratio of the mass of the reaction mass assembly 18to the mass of the stage 14 is between approximately 1:2 and 1:10. Alarger mass ratio is better, but is limited by the physical size of thereaction mass assembly 18.

Preferably, each of the movers in the stage mover assembly 16 and thereaction mover assembly 124, are at the same height along the Z axis. Inthe X axis, the Y stage mover 106, a center of gravity of the devicetable 48, and a center of gravity of the guide assembly 50 arepreferably in line. Also, in the X axis, the Y reaction mover 156 andthe center of gravity of the Y reaction component 33B are preferably inline. In the Y axis, the center of gravity of the device table 48 andthe fluid bearing between the device table 48 and the guide assembly 50are preferably in line. In the Y axis, the center of gravity of thefirst X reaction mass 112, the first X stage mover 98, and the firstupper reaction mover 152A are preferably in line. In the Y axis, thecenter of gravity of the second X reaction mass 114, the second X stagemover 100, and the second upper X reaction mover 152 are preferably inline.

The measurement system 20 monitors movement of each stage 14 relative tothe stage base 12, or to some other reference such as a lens assembly508 (illustrated in FIG. 18). With this information, the stage moverassembly 16 can be used to precisely position of the stages 14. Thedesign of the measurement system 20 can be varied. For example, themeasurement system 20 can utilize laser interferometers, encoders,and/or other measuring devices to monitor the position of the stages 14.

In the embodiment illustrated in FIGS. 1-3, the measurement system 20monitors the position of the device table 48 for each stage 14 along theX axis, along the Y axis, and about the Z axis. For the designillustrated in FIGS. 1-3, for each stage 14, the measurement system 20measures the position of the device table 48 relative to the guideassembly 50 along the Y axis, and the measurement system 20 measures theposition of the device table 48 along the Y axis, along the X axis, andabout the Z axis relative to the lens assembly 508.

In this embodiment, for each stage 14, the measurement system 20utilizes a linear encoder (not shown) that measures the amount ofmovement of device table 48 relative to the guide assembly 50 as thedevice table 48 moves relative to the guide assembly 50. Alternately,for example, an interferometer system (not shown) can be utilized. Asuitable interferometer system can be made with components obtained fromAgilent Technologies in Palo Alto, Calif.

Additionally, for each stage 14, the measurement system 20 includes anXZ interferometer 170 and a Y interferometer 172. The XZ interferometer170 includes an XZ mirror 174 and an XZ block 176. The XZ block 176interacts with the XZ mirror 174 to monitor the location of the devicetable 48 along the X axis and about the Z axis (theta Z). Morespecifically, the XZ block 176 generates a pair of spaced apart XZmeasurement laser beams (not shown) that are reflected off of the XZmirror 174. With these laser beams, the location of the device table 48along the X axis and about the Z axis can be monitored. Further, becausethe device table 48 does not move relative to the guide assembly 50along the X axis or about the Z axis, the location of the guide assembly50 along the X axis and about the Z axis can also be monitored by the XZinterferometer 170.

In the embodiment illustrated in the Figures, the XZ mirror 174 isrectangular shaped and extends along one side of the device table 48.The XZ block 176 is positioned away from the device table 48. The XZblock 176 can be secured to the apparatus frame 46 (illustrated in FIG.18) or some other location that is isolated from vibration.

Somewhat similarly, the Y interferometer 172 includes a Y mirror 178 anda Y block 180. The Y mirror 178 interacts with the Y block 180 tomonitor the position of the device table 48 along the Y axis. Morespecifically, the Y block 180 generates a Y measurement laser beam thatis reflected off of the Y mirror 178. With this laser beam, the locationof the device table 48 along the Y axis can be monitored. Further,because the position of the device table 48 relative to the guideassembly 50 along the Y axis is measured with the encoder, the positionof the guide assembly 50 along the Y axis can also be monitored.

In the embodiment illustrated in the Figures, the Y mirror 178 isrectangular shaped and is positioned along one of the sides of thedevice table 48. The Y block 180 is positioned away from the devicetable 48. The Y block 180 can be secured to the apparatus frame 46(illustrated in FIG. 18) or some other location that is isolated fromvibration.

Additionally, for the embodiment illustrated in FIGS. 5A and 5B, themeasurement system 20 includes one or more sensors (not shown) thatmeasure the position of the upper table component 52 relative to thelower table component 54.

The control system 22 controls the stage mover assembly 16 for eachstage 14 to precisely position the stages 14 and the devices 26. In theembodiment illustrated in FIGS. 1-3, the control system 22 directs andcontrols the current to the conductor array for each of the X stagemover 98, 100 to control movement of the stages 14 along the X axis andabout the Z axis. Similarly, the control system 22 directs and controlsthe current to conductor array for the Y stage mover 106 to controlmovement of the stages 14 along the Y axis. Also, the control system 22directs and controls the current to the conductors of each E/I coreactuator of each Y guide mover 102, 104 to control the position of theguide assembly 50.

Additionally, the control system 22 directs and controls current to thereaction mover assembly 124 to control the position of the reaction massassembly 18 along the X axis, along the Y axis and about the Z axis.More 25 specifically, the control system 22 directs current to theconductor array for each upper X reaction mover 152 to independentlycontrol the position of each X reaction mass 112, 114 relative to thereaction base 42. Further, the control system 22 directs current to theconductor array for each lower X reaction mover 154 and the Y reactionmover 156 to control the position of the reaction base 42 along the Xaxis, along the Y axis and about the Z axis relative to the stage base12.

FIGS. 7A and 7B illustrate simplified schematic top views of a portionof a stage assembly 10 having a single stage 14 that facilitate adiscussion of the movement of the reaction mass assembly 18. Inparticular, FIG. 7A illustrates the stage assembly 10 with one devicetable 48 positioned approximately half-way between the X reaction masses112, 114 along the Y axis. In FIG. 7A, the device table 48 is positionednear a stage assembly combined center of gravity 182 and a stage centerof gravity 184. In this embodiment, the stage assembly combined centerof gravity 182 represents the center of gravity of the device table 48,the guide assembly 50, the first X reaction mass 112, the second Xreaction mass 114, and the reaction base 42 and the stage center ofgravity 184 represents the center of gravity of the device table 48 andthe guide assembly 50. FIG. 7B illustrates the stage assembly 10 withthe guide assembly 50, device table 48, and the stage center of gravity184 positioned away from the stage assembly combined center of gravity182.

The following symbols are used in conjunction with FIGS. 7A and 7B andthe discussion provided below to describe the movement of the reactionmass assembly 18:

L_(y1), represents the distance along the Y axis between the center ofthe first X reaction mass 112 and a stage combined center of gravity184.

L_(y2) represents the distance along the Y axis between the center ofthe second X reaction mass 114 and the stage combined center of gravity184.

L_(yt) represents the distance along the Y axis between the center ofthe first X reaction mass 112 and the center of the second X reactionmass 114.

L_(x) represents the distance along the X axis between the stageassembly combined center of gravity 182 and the stage combined center ofgravity 184.

M_(s) represents the total mass of the stage 14.

M₁ represents the total mass of the first X reaction mass 112.

M₂ represents the total mass of the second X reaction mass 114.

M_(d) represents the total mass of the device table 48.

M_(cm) represents the combined mass of the X reaction masses 112, 114the reaction base 42 and the guide assembly 50.

a^(x) _(s), represents the acceleration of the stage 14 along the Xaxis.

a^(x) ₁, represents the acceleration of the first X reaction mass 112along the X axis.

a^(x) ₂ represents the acceleration of the second X reaction mass 114along the X axis.

a^(Y) _(d) represents the acceleration of the device table 48 along theY axis.

a^(Y) _(cm) represents the acceleration of the X reaction masses 112,114, the reaction base 42, and the guide assembly 50 along the Y axis.

Referring to FIG. 7A, during a move of the stage 14 along the X axis,under the principles of the conservation of momentum, the followingformulas are applicable:Ms∫a ^(x) _(s) dt+M ₁ ∫a ^(x) ₁ dt+M ₂ ∫a ^(x) ₂ dt=constant=0M ₁ a ₁ L _(y1) =M ₂ a ₂ L _(y2)

Referring to FIG. 7B, during a move of the stage 14 along the Y axis,under the principles of conservation of momentum, the following formulasare applicable:M _(d) ∫a ^(Y) _(d) dt+M _(cm) ∫a ^(Y) _(cm) dt=constant=0

Further, to achieve zero torque:M _(d) a ^(Y) _(d) L _(x)=(M ₂ a ^(x) ₂ −M ₁ a ₁ ^(x))L _(yt)

Further, to achieve no net forceM ₁ a ₁ ^(x) +M ₂ a ₂ ^(x)=0

FIG. 7C is a schematic that describes the sensing and control functionsused to move and control a stage assembly 10 that includes the devicetable 48 illustrated in FIGS. 5A and 5B. The sensing and controlfunctions are more thoroughly described in co-pending U.S. patentapplications Ser. Nos. 09/022,713 field Feb. 12, 1998, 09/139,954 filedAug. 25, 1998, and 09/141,762 filed Aug. 27, 1998, each of which ishereby incorporated by reference thereto, in their entireties. Atrajectory 190, or desired path for the focused optical system tofollow, is determined based on the desired path of the wafer or otherobject to which the focused optical system is to be applied. Thetrajectory 190 is next fed into the control system 22. The trajectory190 is compared with a sensor signal vector S that is generated from theoutput of measurement system 20. The difference vector, which resultsfrom the comparison, is transformed to a CG coordinate frame though aninverse transformation 192. The control law 193 prescribes thecorrective action for the signal. The control law may be in the form ofa PID (proportional integral derivative) controller, proportional gaincontroller or preferably a lead-lag filter, or other commonly known lawin the art of control, for example.

The vector for vertical motion is fed to the CG to VCM transformation194. This transforms the CG signal to a value of force to be generatedby the VCMs, which is then fed to the VCM gain 195, and output to thestage hardware 196. The vector for planar motion is fed to the CG toEl-core transformation 197. This transforms the CG signal to a force tobe generated by the El-core force (i.e., electromagnet and targetarrangements). Because the El-core force depends upon the gap squared,it is compensated by the short range sensor vector g through thecompensation block 198, to produce a linear output to the stage hardware196. The stage hardware 196 responds to the input and is measured in thesensor frame S. A similar servo loop (block 199) is not shown in detailfor moving the lower table component 54. The position of lower tablecomponent 54, is also computed using the upper table component 52 andthe gap g. As provided herein, the lower table component 54 is servoedto maintain a predetermined relationship to the upper table component52.

FIGS. 8-10 illustrate a second embodiment having features of the presentinvention. In particular, FIG. 8 illustrates a perspective view of thestage assembly 10, FIG. 9 illustrates a top plan view of the stageassembly 10 of FIG. 8, and FIG. 10 illustrates an exploded perspectiveview of the reaction mass assembly 18. The stage assembly 10 illustratedin FIGS. 8 and 9 includes the stage base 12, a pair of stages 14, thestage mover assembly 16, the reaction mass assembly 18, the measurementsystem 20, and the control system 22.

In the embodiment illustrated in FIGS. 8-9, each stage 14, the stagemover assembly 16, the measurement system 20, and the control system 22are somewhat similar to the equivalent components described above.However, in the embodiment illustrated in FIGS. 8-10, the stage base 12and the reaction mass assembly 18 differ from the embodiment illustratedin FIGS. 1-3.

In the embodiment illustrated in FIGS. 8-10, the X reaction component33A includes the X reaction masses 112, 114. However, in thisembodiment, instead of a reaction base 42, the Y reaction component 33Bincludes a first Y reaction mass 200 and a second Y reaction mass 202.

Further, in this embodiment, the base top 34 of the stage base 12includes a reaction guide assembly 203, e.g. a pair of reaction guides204. Each Y reaction mass 200, 202 includes a Y follower 205. Thereaction guides 204 cooperate with the Y followers 205 to guide movementof the Y reaction masses 200, 202 along the Y axis and allow thereaction masses 112, 114, 200, 202 to move relative to the stage base 12along the Y axis. In the embodiments provided herein, each reactionguide 204 is a rectangular shaped channel in the base top 34 thatextends along the Y axis, and each Y follower 205 is a rectangularshaped lip that extends below each Y reaction mass 200, 202 along the Yaxis. Pressurized fluid is released into the channel and a vacuum iscreated between the stage base 12 and each of the Y reaction masses 200,202 to create a vacuum preload type fluid bearing (not shown). The fluidbearing maintains the Y reaction masses 200, 202 spaced apart from thestage base 12 and allows for relative motion of the reaction masses 112,114, 200, 202 along the Y axis relative to the stage base 12.Alternately, the Y reaction masses 200, 202 can be supported above thestage base 12 by other ways such as magnetic type bearing (not shown) ora ball bearing type assembly (not shown).

In this embodiment, the X reaction masses 112, 114 move independentlyrelative to the Y reaction masses 200, 202 along the X axis. Further,all of the reaction masses 112, 114, 200, 202 move together along the Yaxis. Stated another way, the X reaction masses 112, 114 are rigidlycoupled in the Y direction and move concurrently with the Y reactionmasses 200, 202 along the Y axis.

As can best be seen with reference to FIG. 10, each X reaction mass 112,114 includes a pair of opposed ends 206. Each end 206 includes an Xfollower 208. In this embodiment, each X follower 208 is a notch in theend of the X reaction mass 112, 114. Each of the Y reaction masses 200,202 includes two X guides 210. In this embodiment, each X guide 210 is agroove that is sized and shaped to receive a portion of one of the Xreaction masses 112, 114. The X guides 210 and the X followers 208cooperate to form the mass guide assembly 131. More specifically, the Xguides 210 cooperate with the X followers 208, and allow the X reactionmasses 112, 114 to move relative to the Y reaction masses 200, 202 alongthe X axis. Further, the X guides 210 cooperate with the X followers 208to constraint the X reaction masses 112, 114 so that the X reactionmasses 112, 114 move concurrently with the Y reaction masses 200, 202along the Y axis.

In the design, pressurized fluid is released into each X guide 210 and avacuum is created between each Y reaction mass 200, 202 and each of theX reaction masses 112, 114 to create a vacuum preload type fluid bearing(not shown). The fluid bearing maintains the X reaction masses 112, 114spaced apart from the Y reaction masses 200, 202 and allows for relativemotion of the X reaction masses 112, 114 independently along the X axisrelative to the Y reaction masses 200, 202. Alternately, for example,the X reaction masses 112, 114 can be supported and allowed to moverelative to the Y reaction masses 200, 202 by other ways, such as amagnetic type bearing (not shown) or a ball bearing type assembly (notshown).

Somewhat similar to the embodiment illustrated in FIGS. 1-3, in theembodiment illustrated in FIGS. 8-10, the first component 108 of thefirst X stage mover 98 is secured to and moves with the first X reactionmass 112. Additionally, the first component 108 of the second X stagemover 100 is secured to and moves with the second X reaction mass 114.Further, the first component 108 of the Y stage mover 106 is secured tothe guide assembly 50, and the second component 110 is secured to thedevice table 48. However, in the embodiment illustrated in FIGS. 8-10,each stage 14 utilizes a single Y guide mover 212 to move the guideassembly 50 along the Y axis relative to the stage base 12. In theembodiment illustrated in FIGS. 8-10, the Y guide mover 212 is a pair ofE/I core actuators 214.

In this embodiment, the reaction mover assembly 124 is again used tomake minor corrections along the Y axis to the position of the reactionmass assembly 18 relative to the stage base 12. Further, the reactionmover assembly 124 is used to make minor corrections to the position ofthe X reaction masses 112, 114 along the X axis relative to the Yreaction masses 200, 202 and the stage base 12.

In the embodiment illustrated in FIGS. 8-10, the reaction mover assembly124 includes a pair of X reaction movers 220 and a pair of Y reactionmovers 222 that cooperate to correct the location of the reaction massassembly 18 relative to the stage base 12. In the embodiment illustratedin FIGS. 8-10, each of the reaction movers 220, 222 includes a firstcomponent 224 and an adjacent, second component 226. In the embodimentsprovided herein, one of the components 224, 226 of each of the reactionmovers 220, 222 includes one or more magnet arrays (not shown) and theother component 224, 226 of each of the reaction movers 220, 222includes one or more conductor arrays (not shown).

Electrical current (not shown) is individually supplied to eachconductor array by the control system 22.

For each of the reaction movers 220, 222, the electrical current in eachconductor interacts with a magnetic field (not shown) generated by oneor more of the magnets in the magnet array. This causes a force (Lorentzforce) between the conductors and the magnets.

Specifically, the first component 224 and the second component 226 ofeach X reaction mover 220 interact to independently move one of the Xreaction masses 112, 114 along the X axis relative to the Y reactionmasses 200, 202. In the embodiment illustrated in the FIGS. 8-10, each Xreaction mover 220 is a commutated, linear motor. For one of the Xreaction movers 220, the first component 224 is secured to the first Xreaction mass 112 while the second component 226 is secured to either orboth of the Y masses 200, 202. Similarly, for the other X reaction mover220, the first component 224 is secured to the second X reaction mass114 while the second component 226 is secured to either or both of the Ymasses 200, 202.

In the embodiment illustrated in FIGS. 8-10, a first connector bracket228 and a spaced apart second connector bracket 230 each extend betweenthe Y masses 200, 202. The connector brackets 228, 230 move with the Ymasses 200, 202 above the stage base 12. The first connector bracket 228extends along the first X reaction mass 112 and the second connectorbracket 230 extends along the second X reaction mass 114. In thisembodiment, the second component 226 of each of the X reaction movers220 is secured to the connector brackets 228, 230.

In FIGS. 8-10, the first component 224 of each X reaction mover 220includes a pair of spaced apart magnet arrays (not shown), while thesecond component 226 of each X reaction mover 220 includes a conductorarray (not shown). With this desigh, the X reaction movers 220 canindependently make corrections to the positions of the X reaction masses112, 114 along the X axis relative to the stage base 12. Alternately,for example, the first component of each X reaction mover could includea conductor array while the second component of each X reaction movercould include a pair of spaced apart magnet arrays.

Preferably, the X reaction movers 220 include a measurement device (notshown) such as an encoder that provides information regarding theposition of the X reaction masses 112, 114 relative to the stage base 12or the Y masses 200, 202 along the X axis.

Somewhat similarly, the first component 224 and the second component 226of each Y reaction mover 222 interact to selectively move the reactionmasses 112, 114, 200, 202 along the Y axis relative to the stage base12. In the embodiment illustrated in FIGS. 8-10, each Y reaction mover222 is a commutated, linear motor. For each of the Y reaction movers222, the first component 224 is secured to one of the Y reaction masses200, 202 while the second component 226 is secured to the stage base 12.

In FIGS. 8-10, the first component 224 of each Y reaction mover 222includes a pair of spaced apart magnet arrays (not shown) while thesecond component of each Y reaction mover includes a conductor array(not shown). With this design, the Y reaction movers 222 can make minorcorrections to the positions of the reaction masses 112, 114, 200, 202along the Y axis relative to the stage base 12. Alternately, forexample, the first component 224 of each Y reaction mover 222 couldinclude a conductor array while the second component 226 of each Yreaction mover 222 could include a pair of spaced apart magnet arrays.

Preferably, the Y reaction movers 222 include a measurement device (notshown) such as an encoder that provides information regarding theposition of the Y reaction masses 200, 202 relative to the stage base 12along the Y axis.

Alternately, in this embodiment, the second component 226 of eachreaction mover 220, 222 could be secured to the mounting base 24 withthe ground frame 164 (illustrated in FIG. 18) instead of to the stagebase 12.

FIGS. 11-13 illustrate a third embodiment having features of the presentinvention. In particular, FIG. 11 illustrates a perspective view of thestage assembly 10, FIG. 12 illustrates a perspective view of thereaction mass assembly 18, and FIG. 13 illustrates an explodedperspective view of the reaction mass assembly 18. The stage assembly 10illustrated in FIG. 11 includes the stage base 12, a pair of stages 14,the stage mover assembly 16, the reaction mass assembly 18, and thecontrol system 22. The measurement system is not illustrated in FIG. 11.

In the embodiment illustrated in FIG. 11, each stage 14, the stage moverassembly 16, and the control system 22 are somewhat similar to theequivalent components described above. However, in the embodimentillustrated in FIGS. 11-13, the stage base 12 and the reaction massassembly 18 differ from the embodiment illustrated in FIGS. 1-3 and theembodiment illustrated in FIGS. 8-10.

In the embodiment illustrated in FIGS. 11-13, the X reaction component33A includes the X reaction masses 112, 114. However, in thisembodiment, instead of a reaction base, the Y reaction component 33Bincludes a reaction frame 300.

As can best be seen with reference to FIGS. 12 and 13, in thisembodiment, the stage base 12 is somewhat rectangular shaped andincludes a front lip 302, a rear lip 304, a raised central section 306,and a pair of spaced apart upper edge sections 307. The front lip 302cantilevers away from a front side of the stage base 12, and the rearlip 304 cantilevers away from a rear side of the stage base 12. Theraised central section 306 separates the upper edge sections 307. Theraised central section 306 includes a pair of spaced apart section sides309.

The reaction frame 300 is rectangular frame shaped and includes a firstframe side 308, a second frame side 310, a front frame side 312, and arear frame side 314. Referring to FIG. 13, the first and second framesides 308, 310 are offset from and are positioned above the front andrear frame sides 312, 314. This feature enhances the access to thestages 14.

The first frame side 308 and the second frame side 310 each include an Xmass guide 316 for guiding the X reaction masses 112, 114. Each Xreaction mass 112, 114 includes an X follower 318. The X mass guides 316and the X followers 318 cooperate to form the mass guide assembly 131.In this embodiment, each X mass guide 316 cooperates with the X follower318 of one of the X reaction masses 112, 114, to guide the movement ofthe X reaction masses 112, 114 along the X axis relative to the reactionframe 300 and stage base 12. In the embodiments provided herein, thefirst and second frame sides 308, 310 are each somewhat rectangular beamshaped and each X follower 318 is a channel that extends along the Xaxis in each of the X reaction masses 112, 114. The front and rear framesides 312, 314 are also generally rectangular shaped.

Pressurized fluid is released and a vacuum is created between the firstand second frame sides 308, 310 and the X reaction masses 112, 114 tocreate a vacuum preload type fluid bearing (not shown). The vacuumpreload type fluid bearing maintains the X reaction masses 112, 114spaced apart from the reaction frame 300 and allows for independentrelative motion of the X reaction masses 112, 114 along the X axisrelative to the reaction frame 300 and stage base 12. Alternately, the Xreaction masses 112, 114 can be supported above the reaction frame 300by other ways such as a magnetic type bearing (not shown) or a ballbearing type assembly (not shown).

It should be noted in this embodiment, that the X reaction masses 112,114 and the reaction frame 300 move concurrently along the Y axis.

In the design provided in FIGS. 11-13, the first frame side 308 and thesecond frame side 310 are positioned above the upper edge sections 307and are separated by the raised central section 306. Further, the frontframe side 312 is positioned below the front lip 302, and the rear frameside 314 is positioned below the rear lip 304. In the embodimentillustrated in FIGS. 11-13, the reaction frame 300 is maintained abovethe stage base 12 with a reaction guide assembly 203. More specifically,in this embodiment, pressurized fluid (not shown) is released and avacuum is pulled in fluid inlets (not shown) to create a vacuum preloadtype fluid bearing between the stage base 12 and the reaction frame 300.The vacuum preload type, fluid bearing maintains the reaction frame 300spaced apart from the stage base 12 along the X axis and along the Zaxis. With this design, the vacuum preload type fluid bearing allows formotion of the reaction frame 300 along the Y axis relative to the stagebase 12. Further, the fluid bearing inhibits movement of the reactionframe 300 relative to the stage base 12 along the X axis, along the Zaxis, and about the X, Y and Z axis.

Alternately, the reaction frame 300 can be supported spaced apart fromthe stage base 12 by other ways. For example, a magnetic type bearing(not shown) or a ball bearing type assembly (not shown) could beutilized that allows for motion of the reaction frame 300 relative tothe stage base 12.

Somewhat similar to the embodiment illustrated in FIGS. 1-3, in thisembodiment, the first component 108 of the first X stage mover 98 issecured to and moves with the first X reaction mass 112; and, the firstcomponent 108 of the second X stage mover 100 is secured to and moveswith the second X reaction mass 114.

Further, the stage assembly 10 illustrated in FIG. 11 includes a single,Y guide mover (not shown) that moves the guide assembly 50 along the Yaxis relative to the stage base 12. In this embodiment, the reactionmover assembly 124 is used to make minor corrections along the Y axis tothe position of the reaction mass assembly 18 relative to the stage base12. Further, the reaction mover assembly 124 is used to independentlymake corrections to the position of the X reaction masses 112, 114 alongthe X axis relative to the reaction frame 300.

In the embodiment illustrated in FIGS. 11-13, the reaction moverassembly 124 includes a first X reaction mover 320, a second X reactionmover 322, a first Y reaction mover 324, and a second Y reaction mover326, that cooperate to move the reaction mass assembly 18 relative tothe stage base 12.

Each of the reaction movers 320, 322, 324, 326 includes a firstcomponent 328 and an adjacent, second component 330. In the embodimentsprovided herein, one of the components 328, 330 of each reaction mover320, 322, 324, 326 includes one or more magnet arrays (not shown) andthe other component 328, 330 of each mover 320, 322, 324, 326 includesone or more conductor arrays (not shown). Electrical current (not shown)is individually supplied to each conductor array by the control system22. For each reaction mover 320, 322, the electrical current in eachconductor interacts with a magnetic field (not shown) generated by oneor more of the magnets in the magnet array. This causes a force (Lorentzforce) between the conductors and the magnets.

Specifically, in the embodiment illustrated in the FIGS. 11-13, each Xreaction mover 320, 322 is a commutated, linear motor. For the first Xreaction mover 320, the first component 328 is secured to the first Xreaction mass 112 while the second component 330 is secured to the firstframe side 308 of the reaction frame 300. Similarly, for the second Xreaction mover 322, the first component 328 is secured to the second Xreaction mass 114 while the second component 330 is secured to thesecond frame side 310 of the reaction frame 300.

It should be noted in this embodiment that each X reaction mass 112, 114includes a mass aperture 332, and that the second component 330 of eachX reaction mover 320, 322 extends through the mass aperture 332.

In this embodiment, the first component 328 of each X reaction mover320, 322 includes a pair of spaced apart magnet arrays (not shown) whilethe second component 330 of each X reaction mover 320, 322 includes aconductor array (not shown). With this design, the X reaction movers320, 322 can make minor corrections to the positions of the X reactionmasses 112, 114 along the X axis relative to the reaction frame 300 andthe stage base 12. Alternately, for example, the first component of eachX reaction mover could include a conductor array while the secondcomponent of each X reaction mover could include a pair of spaced apartmagnet arrays.

Preferably, the X reaction movers 320, 322 include a measurement device(not shown) such as an encoder that provides information regarding theposition of the X reaction masses 112, 114 relative to the reactionframe 300 and the stage base 12 along the X axis.

Somewhat similarly, in the embodiment illustrated in FIGS. 11-13, each Yreaction mover 324, 326 is a commutated, linear motor. For each of the Yreaction movers 324, 326, the first component 328 is secured to thereaction frame 300, while the second component 330 is secured to thestage base 12 or preferably to the mounting base 24. More specifically,for the first Y reaction mover 324, the first component 328 is securedto the front frame side 312, and the second component 330 is secured tothe front lip 302. Similarly, for the second Y reaction mover 326, thefirst component 328 is secured to the rear frame side 314, and thesecond component 330 is secured to the rear lip 304.

In this embodiment, the first component 328 of each Y reaction mover324, 326 includes a pair of spaced apart magnet arrays (not shown) whilethe second component 330 of each Y reaction mover 324, 326 includes aconductor array (not shown). With this design, the Y reaction movers324, 326 can make minor corrections to the position of the reactionframe 300 and the X reaction masses 112, 114 along the Y axis relativeto the stage base 12. Alternately, for example, the first component ofeach Y reaction mover could include a conductor array while the secondcomponent of each Y reaction mover could include a pair of spaced apartmagnet arrays.

Preferably, the Y reaction movers 324, 326 include a measurement device(not shown) such as an encoder that provides information regarding theposition of the reaction frame 300 relative to the stage base 12 alongthe Y axis.

FIGS. 14-16 illustrate a fourth embodiment having features of thepresent invention. In particular, FIG. 14 illustrates a perspective viewof the stage assembly 10, FIG. 15 illustrates a perspective view of thereaction mass assembly 18, and FIG. 16 illustrates an explodedperspective view of the reaction mass assembly 18. The stage assembly 10illustrated in FIG. 14 includes the stage base 12, a pair of stages 14,the stage mover assembly 16, the reaction mass assembly 18, and thecontrol system 22. The measurement system is not illustrated in FIG. 14.

In the embodiment illustrated in FIG. 14, each stage 14, the stage moverassembly 16, and the control system 22 are somewhat similar to theequivalent components described above. Further, the stage base 12 andthe reaction mass assembly 18 illustrated in FIGS. 14-16 are similar tothe stage base 12 and reaction mass assembly 18 illustrated in FIGS.11-13 and described above. However, in the embodiment illustrated inFIGS. 14-16, the reaction frame 300 is free to move along the X axis,along the Y axis, and about the Z axis relative to the stage base 12.More specifically, in the embodiment, the fluid bearing between thereaction frame 300 and the stage base 12 only maintains the reactionframe 300 spaced apart along the Z axis relative to the stage base 12.Stated another way, the fluid bearing allows for motion of the reactionframe 300 along the X axis, along the Y axis, and about the Z axisrelative to the stage base 12.

Further, in the embodiment illustrated in FIGS. 14-16, the reactionmover assembly 124 differs from the reaction mover assembly 124illustrated in FIGS. 11-13 and described above. In particular, in theembodiment illustrated in FIGS. 14-16, the reaction mover assembly 124includes the X reaction movers 320, 322, a first Y reaction mover 350, asecond Y reaction mover 352, and a lower X reaction mover 354 thatcooperate to move the reaction mass assembly 18 relative to the stagebase 12.

In this embodiment, the reaction mover assembly 124 makes minorcorrections along the X axis, along the Y axis, and about the Z axis tothe position of the reaction frame 300 relative to the stage base 12.Further, the reaction mover assembly 124 makes independent correctionsto the position of the X reaction masses 112, 114 along the X axisrelative to the reaction frame 300.

The first and second X reaction movers 320, 322 are the same asillustrated in FIGS. 11-13 and described above. Each Y reaction mover350, 352, and the lower X reaction mover 354 includes a first component356 and an adjacent second component 358. One of the components of eachreaction mover 350, 352, 354 includes one or more magnet arrays (notshown) and the other component of each reaction mover 350, 352, 354includes one or more conductor arrays (not shown). Electrical current(not shown) is individually supplied to each conductor array by thecontrol system 22. For each reaction mover 350, 352, 354, the electricalcurrent in each conductor interacts with a magnetic field (not shown)generated by one or more of the magnets in the magnet array. This causesa force (Lorentz force) between the conductors and the magnets.

In the embodiment illustrated in the FIGS. 14-16, each Y reaction mover350, 352 is a commutated linear motor. For the first Y reaction mover350, the first component 356 is secured to the front frame side 312 ofthe reaction frame 300, while the second component 358 is secured to themounting base 24 (illustrated in FIG. 18) with a first reaction moverframe 360. Similarly, for the second Y reaction mover 352, the firstcomponent 356 is secured to the rear frame side 314 of the reactionframe 300, and the second component 358 is secured to the mounting base24 with a second reaction mover frame 362. Only a portion of eachreaction mover frame 360, 362 is illustrated in FIGS. 14-16.

In this embodiment, the first component 356 of each Y reaction mover350, 352, includes a pair of magnet arrays (not shown) while the secondcomponent 358 of each Y reaction mover 350, 352 includes a conductorarray (not shown). With this design, the Y reaction movers 350, 352 canmake minor corrections to the positions of the X reaction masses 112,114 and the reaction frame 300 along the Y axis and about the Z axisrelative to the stage base 12. Alternately, for example, the firstcomponent of each Y reaction mover could include a conductor array whilethe second component of each Y reaction mover could include a pair ofspaced apart magnet arrays.

Preferably, the Y reaction movers 350, 352 include a measurement device(not shown) such as an encoder that provides information regarding theposition of the X reaction frame 300 relative to the stage base 12.

Somewhat similarly, the first component 356 and the second component 358of the lower X reaction mover 354 interact to selectively move thereaction frame 300 along the X axis relative to the stage base 12. Inthe embodiment illustrated in FIGS. 14-16, the lower X reaction mover354 is a non-commutated voice coil motor. In this embodiment, for thelower X reaction mover 354, the first component 356 is secured to thefront frame side 312 of the reaction frame 300, while the secondcomponent 358 is secured to the mounting base 24 with a third reactionmover frame 364.

In this embodiment, the first component 356 of the lower X reactionmover 354 includes a pair of spaced apart magnet arrays (not shown)while the second component 358 includes a conductor array (not shown).With this design, the lower X reaction mover 354 can make minorcorrections to the position of the reaction frame 300 and the X reactionmasses 112, 114 along the X axis relative to the stage base 12.Alternately, for example, the first component of the lower X reactionmover could include a conductor array while the second component of eachY reaction mover could include a pair of spaced apart magnet arrays.

Preferably, the lower X reaction mover 354 includes a measurement device(not shown) such as an encoder that provides information regarding theposition of the reaction frame 300 relative to the stage base 12 alongthe X axis.

Although it is not presently preferred, the second component 358 of thefirst Y reaction mover 350, the second Y reaction mover 352 and lower Xreaction mover 354 could be attached to the stage base 12.

As discussed above, the control system 22 directs and controls currentto the reaction mover assembly 124 to control the position of thereaction mass assembly 18 relative to the stage base 12. Preferably, thecontrol system 22 controls current to the reaction mover assembly 124 toprevent the X reaction masses 112, 114 from achieving a constantvelocity, and to keep the stroke of the reaction movers relativelyshort. Stated another way, the control system 22 controls current to thereaction mover assembly 124 to: (i) correct external disturbances thatcan influence the position of the reaction mass assembly 18, (ii) toprevent the X reaction masses 112, 114 from drifting off of the stagebase 12, (iii) to prevent unwanted motion of the assembly's center ofgravity 182, (iv) to prevent the exposure apparatus 30 from moving, and(v) to correct any torque that is transferred to the reaction massassembly 18.

Basically, the control system 22 controls current to the reaction moverassembly 124 to ensure that the X reaction masses 112, 114 and the restof the reaction mass assembly 18 are properly positioned and/or centeredrelative to the stage base 12.

The control system 22 can control and direct current to the reactionmover assembly 124 at any time during the operation of the stageassembly 10 to correct the position of the X reaction masses 112, 114and the rest of the reaction mass assembly 18. As provided herein, thecontrol system 22 and the reaction mover assembly 124 can continuouslyservo the reaction mass assembly 18 so that the reaction mass assembly18 is centered on the stage base 12.

Preferably, the control system 22 controls and directs current to thereaction mover assembly 124 in a way that minimizes the disturbancescreated by the reaction mover assembly 124 on the stage assembly 10 andthe exposure apparatus 30. More specifically, the timing and/or theamount of current from the control system 22 directed to the reactionmover assembly 124 can be varied to minimize the influence of thedisturbances created by the reaction mover assembly 124 on the stageassembly 10. Further, the timing and/or the amount of current can bevaried according to the use of the stage assembly.

In a first embodiment, for an exposure apparatus 30, the control system22 can control and direct current to the reaction mover assembly 124 sothat the reaction movers only move and correct the position of thereaction mass assembly 18 at selected times. For example, the reactionmovers can be activated between exposures of the exposure apparatus 30and deactivated during an exposure. Stated another way, for the exposureapparatus 30, the control system 22 can be designed to direct current tothe reaction mover assembly 124 only when an illumination system 504(illustrated in FIG. 18) is not directing a beam of light energy at thereticle 32.

In this embodiment, the control system 22 can direct current to thereaction mover assembly 124 between each chip (not shown) on thesemiconductor wafer 28, between each row of chips on the semiconductorwafer 28, between every scan of the semiconductor wafer 28, or betweeneach semiconductor wafer 28 processed by the exposure apparatus 30.Stated another way, the reaction mover assembly 124 can be activated tomove the reaction mass assembly 18 between each chip (not shown) on thesemiconductor wafer 28, between each row of chips on the semiconductorwafer 28, between every scan of the semiconductor wafer 28, or betweeneach semiconductor wafer 28 processed by the exposure apparatus 30.

Because the reaction mover assembly 124 is not activated during anexposure, the disturbances created by the reaction mover assembly 124 onthe stage assembly 10 during exposure are minimized.

In another embodiment of the control system 22, the rate of movement ofthe reaction movers is varied according to the operation of the stageassembly 10. For example, for an exposure apparatus 30, the controlsystem 22 can control and direct current to the reaction mover assembly124 at a different rate during an exposure than between exposures of theexposure apparatus 30. For example, during an exposure, the controlsystem 22 can direct current to the reaction mover assembly 124 so thatthe forces generated by the reaction mover assembly 124 are relativelysmall and the gain is low. Alternately, between exposures, the controlsystem 22 can direct current to the reaction mover assembly 124 so thatthe forces generated by the reaction mover assembly 124 are relativelylarge and the gain is high.

Stated another way, for the exposure apparatus 30, the control system 22can be designed to direct a relatively large current to the reactionmover assembly 124 only when an illumination system 504 (illustrated inFIG. 18) is not directing a beam of light energy at the reticle 32.

As provided herein, the control system 22 can direct a relatively largecurrent to the reaction mover assembly 124 between each chip (not shown)on the semiconductor wafer 28, between each row of chips on thesemiconductor wafer 28, between every scan of the wafer 28, or betweeneach semiconductor wafer 28 processed by the exposure apparatus 30. Withthis design, the control system 22 changes the closed loop bandwidthbetween exposures. Stated another way, the reaction mover assembly 124can make relatively large adjustments to the position of the reactionmass assembly 18 between each chip (not shown) on the wafer 28, betweeneach row of chips on the semiconductor wafer 28, between every scan ofthe semiconductor wafer 28, or between each semiconductor wafer 28processed by the exposure apparatus 30. Alternately, the reaction moverassembly 124 makes relatively small adjustments to the position on thereaction mass assembly 18 during an exposure.

Because the reaction mover assembly 124 makes relatively smalladjustments to the position on the reaction mass assembly 18 during anexposure, the disturbances created by the reaction mover assembly 124 onthe stage assembly 10 during exposure are minimized.

FIG. 17A illustrates a simplified schematic top view of a portion of astage assembly 10 having a single stage 14 to facilitate a discussion ofthe control system 22. In particular, FIG. 17A illustrates the stageassembly 10 with one device table 48 positioned approximately half-waybetween the X reaction masses 112, 114 along the Y axis. In FIG. 17A,the device table 48 is positioned near the center of gravity 400 of thestage assembly 10.

The following symbols are used in conjunction with FIG. 17A and thediscussion provided below to describe the movement of the reaction massassembly 18:

L_(YM) represents the distance along the Y axis between the center ofthe first X stage mover 98 and the second X stage mover 100.

L_(CG) represents the distance along the Y axis between a stage assemblycenter of gravity 400 and a stage center of gravity 402.

P_(M1) represents the momentum of the first X reaction mass 112 alongthe X axis.

P_(M2) represents the momentum of the second X reaction mass 114 alongthe X axis.

F_(S1) represents the force generated by the first X stage mover 98(illustrated in phantom in FIG. 17A).

F_(S2) represents the force generated by the second X stage mover 100.

F_(r1) represents the force generated by the first X reaction mover 404.

F_(r2) represents the force generated by the second X reaction mover406.

The two equations that define the X stage mover 98, 100 force balanceareF _(S1) +F _(S2) =F _(x)  Force equationF _(S1)(L _(YM)/2+L _(CG))−F _(S2)(L _(YM)/2−L _(CG))=0  Moment equation

Solving these two equations leads toF _(S1) =F _(x)/2−[F _(x) L _(CG) /][L _(YM) ]F _(S2) =F _(x)/2+[F _(x)L _(CG) ]/[L _(CG) [/]L _(YM])

For each X reaction mass 112, 114, the total momentum (mxv) is equal tothe time integral of the forces acting on it. Each X reaction mass 112,114 has a reaction force generated by one of the X stage movers 98, 100and a corrective force generated by one of the X reaction movers 404,406.P ₁ =m ₁ V ₁=∫(F _(S1) +F _(r1))dt

It is assumed that the first X reaction mover 404 and the second Xreaction mover 406 are driven in opposite directions with the sameamplitude.F_(r1=F) _(r2)=F_(t)

A similar equation applies to the second X reaction mass 114.Substituting the previous result into these equations leads to:

 P ₁=∫(F _(x)/2)dt−1/2L _(ym)(∫F _(x) L _(CG) dt)+∫F _(r1) dtP ₂=∫(F _(x)/2)dt+1/2L _(ym)(∫F _(x) L _(CG) dt)+∫F _(r2) dt

These equations show that the momentum of each X reaction mass 112, 114is one-half the stage 14 momentum, plus a term that depends on the timehistory of F_(x) and L_(CG), and the time integral of the reaction mover404, 406 force. To ensure that the X reaction masses 112, 114 are notleft with a constant velocity when the stage 14 returns to zerovelocity, the second and third terms must cancel. This leads to thefollowing equation:∫F _(t) dt=1/(2Lym)∫F _(x) L _(CG) dt  (equation 1)

One easy solution to this integral equation is to letF _(t) =F _(x) L _(CG)/(2Lym)

But this transmits the high frequency components of F_(x) through thereaction movers 404, 406. Ideally, the F_(t) would only have lowfrequency components.

FIG. 17B is a schematic that describes a method for reducing thefrequency content of F_(t). An input 408 is equal to F_(x)(L_(CG)/2Lym).The low frequency components of this input signal pass through low passfilter 412 to summing junction 416. The output of summing junction 416is the reaction force F_(t). The input signal 408 also goes tointegrator 410, which calculates the time integral∫F_(x)(L_(CG)/2Lym)dt.

A second integrator 418 integrates the output signal 420, and producesthe time integral ∫F_(t)dt. A differencing junction 414 calculates anerror signal which is the difference between the outputs of integrator410 and second integrator 418. Compensator 415 performs a calculation(such as multiplying by a gain K) on the error signal to produce acorrection signal that is added to the output of low pass filter 412 insumming junction 416 to produce the output signal 420. By adjusting thecutoff frequency of the low pass filter 412 and the compensationcalculation 415, the frequency content of output 420 can be limited toany desired value. The feedback loop through integrator 418 anddifferencing junction 414 ensures that over time, the two integrals areequal and equation 1 is satisfied.

FIG. 18 is a schematic view illustrating an exposure apparatus 30 usefulwith the present invention. The exposure apparatus 30 includes theapparatus frame 46, the ground frame 164, an illumination system 504(irradiation apparatus), a reticle stage assembly 506, a lens assembly508, and a wafer stage assembly 510. The stage assemblies 10 providedherein can be used as the wafer stage assembly 510. Alternately, withthe disclosure provided herein, the stage assembly 10 provided hereincan be modified for use as the reticle stage assembly 506.

The exposure apparatus 30 is particularly useful as a lithographicdevice that transfers a pattern (not shown) of an integrated circuitfrom the reticle 32 onto the semiconductor wafer 28. The exposureapparatus 30 mounts to the mounting base 24, e.g., the ground, a base,or floor or some other supporting structure.

The apparatus frame 46 is rigid and supports the components of theexposure apparatus 30. The design of the apparatus frame 46 can bevaried to suit the design requirements for the rest of the exposureapparatus 30. The apparatus frame 46 illustrated in FIG. 18 supports thelens assembly 508 and the illumination system 504 and the reticle stageassembly 506 above the mounting base 24.

The illumination system 504 includes an illumination source 512 and anillumination optical assembly 514. The illumination source 512 emits abeam (irradiation) of light energy. The illumination optical assembly514 guides the beam of light energy from the illumination source 512 tothe lens assembly 508. The beam illuminates selectively differentportions of the reticle 32 and exposes the semiconductor wafer 28. InFIG. 18, the illumination source 512 is illustrated as being supportedabove the reticle stage assembly 506. Typically, however, theillumination source 512 is secured to one of the sides of the apparatusframe 46 and the energy beam from the illumination source 512 isdirected to above the reticle stage assembly 506 with the illuminationoptical assembly 514.

The lens assembly 508 projects and/or focuses the light passing throughthe reticle to the wafer. Depending upon the design of the exposureapparatus 30, the lens assembly 508 can magnify or reduce the imageilluminated on the reticle 32.

The reticle stage assembly 506 holds and positions the reticle relativeto the lens assembly 508 and the wafer. Similarly, the wafer stageassembly 510 holds and positions the wafer with respect to the projectedimage of the illuminated portions of the reticle 32. In FIG. 18, thewafer stage assembly 510 utilizes a stage assembly 10 having features ofthe present invention. Depending upon the design, the exposure apparatus30 can also include additional motors to move the stage assemblies 506,510.

There are a number of different types of lithographic devices. Forexample, the exposure apparatus 30 can be used as scanning typephotolithography system that exposes the pattern from the reticle 32onto the wafer 28 with the reticle 32 and the wafer 28 movingsynchronously. In a scanning type lithographic device, the reticle 32 ismoved perpendicular to an optical axis of the lens assembly 508 by thereticle 32 stage assembly 506 and the wafer 28 is moved perpendicular toan optical axis of the lens assembly 508 by the wafer 28 stage assembly510. Scanning of the reticle 32 and the wafer 28 occurs while thereticle and the wafer 28 are moving synchronously.

Alternately, the exposure apparatus 30 can be a step-and-repeat typephotolithography system that exposes the reticle 32 while the reticle 32and the wafer 28 are stationary. In the step and repeat process, thewafer 28 is in a constant position relative to the reticle 32 and thelens assembly 508 during the exposure of an individual field.Subsequently, between consecutive exposure steps, the wafer 28 isconsecutively moved by the wafer stage assembly 510 perpendicular to theoptical axis of the lens assembly 508 so that the next field of thewafer 28 is brought into position relative to the lens assembly 508 andthe reticle 32 for exposure. Following this process, the images on thereticle 32 are sequentially exposed onto the fields of the wafer 28 sothat the next field of the wafer 28 is brought into position relative tothe lens assembly 508 and the reticle 32.

However, the use of the exposure apparatus 30 provided herein is notlimited to a photolithography system for semiconductor manufacturing.The exposure apparatus 30, for example, can be used as an LCDphotolithography system that exposes a liquid crystal display devicepattern onto a rectangular glass plate or a photolithography system formanufacturing a thin film magnetic head. Further, the present inventioncan also be applied to a proximity photolithography system that exposesa mask pattern by closely locating a mask and a substrate without theuse of a lens assembly. Additionally, the present invention providedherein can be used in other devices, including other semiconductorprocessing equipment, machine tools, metal cutting machines, andinspection machines.

The illumination source 512 can be g-line (436 nm), i-line (365 nm), KrFexcimer laser (248 nm), ArF excimer laser (193 nm) and F₂ laser (157nm). Alternately, the illumination source 512 can also use chargedparticle beams such as an x-ray and electron beam. For instance, in thecase where an electron beam is used, thermionic emission type lanthanumhexaboride (LaB₆) or tantalum (Ta) can be used as an electron gun.Furthermore, in the case where an electron beam is used, the structurecould be such that either a mask is used or a pattern can be directlyformed on a substrate without the use of a mask.

In terms of the magnification of the lens assembly 508 included in thephotolithography system, the lens assembly 508 need not be limited to areduction system. It could also be a 1× or magnification system.

With respect to a lens assembly 508, when far ultra-violet rays such asthe excimer laser is used, glass materials such as quartz and fluoritethat transmit far ultra-violet rays is preferable to be used. When theF₂ type laser or x-ray is used, the lens assembly 508 should preferablybe either catadioptric or refractive (a reticle should also preferablybe a reflective type), and when an electron beam is used, electronoptics should preferably consist of electron lenses and deflectors. Theoptical path for the electron beams should be in a vacuum.

Also, with an exposure device that employs vacuum ultra-violet radiation(VUV) of wavelength 200 nm or lower, use of the catadioptric typeoptical system can be considered. Examples of the catadioptric type ofoptical system include the disclosure Japan Patent ApplicationDisclosure No.8-171054 published in the Official Gazette for Laid-OpenPatent Applications and its counterpart U.S. Pat. No. 5,668,672, as wellas Japan Patent Application Disclosure No.10-20195 and its counterpartU.S. Pat. No. 5,835,275. In these cases, the reflecting optical devicecan be a catadioptric optical system incorporating a beam splitter andconcave mirror. Japan Patent Application Disclosure No.8-334695published in the Official Gazette for Laid-Open Patent Applications andits counterpart U.S. Pat. No. 5,689,377 as well as Japan PatentApplication Disclosure No.10-3039 and its counterpart U.S. patentapplication Ser. No. 873,605 (Application Date: Jun. 12, 1997) also usea reflecting-refracting type of optical system incorporating a concavemirror, etc., but without a beam splitter, and can also be employed withthis invention. As far as is permitted, the disclosures in theabove-mentioned U.S. patents, as well as the Japan patent applicationspublished in the Official Gazette for Laid-Open Patent Applications areincorporated herein by reference.

Further, in photolithography systems, when linear motors (see U.S. Pat.Nos. 5,623,853 or 5,528,118) are used in a wafer stage or a mask stage,the linear motors can be either an air levitation type employing airbearings or a magnetic levitation type using Lorentz force or reactanceforce. Additionally, the stage could move along a guide, or it could bea guideless type stage that uses no guide. As far as is permitted, thedisclosures in U.S. Pat. Nos. 5,623,853 and 5,528,118 are incorporatedherein by reference.

Alternatively, one of the stages could be driven by a planar motor,which drives the stage by an electromagnetic force generated by a magnetunit having two-dimensionally arranged magnets and an armature coil unithaving two-dimensionally arranged coils in facing positions. With thistype of driving system, either the magnet unit or the armature coil unitis connected to the stage and the other unit is mounted on the movingplane side of the stage.

Movement of the stages as described above generates reaction forces thatcan affect performance of the photolithography system. Reaction forcesgenerated by the wafer (substrate) stage motion can be mechanicallyreleased to the floor (ground) by use of a frame member as described inU.S. Pat. No. 5,528,118 and published Japanese Patent ApplicationDisclosure No. 8-166475. Additionally, reaction forces generated by thereticle (mask) stage motion can be mechanically released to the floor(ground) by use of a frame member as described in U.S. Pat. No.5,874,820 and published Japanese Patent Application Disclosure No.8-330224. As far as is permitted, the disclosures in U.S. Pat. No. Nos.5,528,118 and 5,874,820 and Japanese Patent Application Disclosure No.8-330224 are incorporated herein by reference.

As described above, a photolithography system according to the abovedescribed embodiments can be built by assembling various subsystems,including each element listed in the appended claims, in such a mannerthat prescribed mechanical accuracy, electrical accuracy, and opticalaccuracy are maintained. In order to maintain the various accuracies,prior to and following assembly, every optical system is adjusted toachieve its optical accuracy. Similarly, every mechanical system andevery electrical system are adjusted to achieve their respectivemechanical and electrical accuracies. The process of assembling eachsubsystem into a photolithography system includes mechanical interfaces,electrical circuit wiring connections and air pressure plumbingconnections between each subsystem. Needless to say, there is also aprocess where each subsystem is assembled prior to assembling aphotolithography system from the various subsystems. Once aphotolithography system is assembled using the various subsystems, atotal adjustment is performed to make sure that accuracy is maintainedin the complete photolithography system. Additionally, it is desirableto manufacture an exposure system in a clean room where the temperatureand cleanliness are controlled.

Further, semiconductor devices can be fabricated using the abovedescribed systems, by the process shown generally in FIG. 19. In step601 the device's function and performance characteristics are designed.Next, in step 602, a mask (reticle) having a pattern is designedaccording to the previous designing step, and in a parallel step 603 awafer is made from a silicon material. The mask pattern designed in step602 is exposed onto the wafer from step 603 in step 604 by aphotolithography system described hereinabove in accordance with thepresent invention. In step 605 the semiconductor device is assembled(including the dicing process, bonding process and packaging process),finally, the device is then inspected in step 606.

FIG. 20 illustrates a detailed flowchart example of the above-mentionedstep 604 in the case of fabricating semiconductor devices. In FIG. 20,in step 611 (oxidation step), the wafer surface is oxidized. In step 612(CVD step), an insulation film is formed on the wafer surface. In step613 (electrode formation step), electrodes are formed on the wafer byvapor deposition. In step 614 (ion implantation step), ions areimplanted in the wafer. The above mentioned steps 611-614 form thepreprocessing steps for wafers during wafer processing, and selection ismade at each step according to processing requirements.

At each stage of wafer processing, when the above-mentionedpreprocessing steps have been completed, the following post-processingsteps are implemented. During post-processing, first, in step 615(photoresist formation step), photoresist is applied to a wafer. Next,in step 616 (exposure step), the above-mentioned exposure device is usedto transfer the circuit pattern of a mask (reticle) to a wafer. Then instep 617 (developing step), the exposed wafer is developed, and in step618 (etching step), parts other than residual photoresist (exposedmaterial surface) are removed by etching. In step 619 (photoresistremoval step), unnecessary photoresist remaining after etching isremoved.

Multiple circuit patterns are formed by repetition of thesepreprocessing and post-processing steps.

A further embodiment of the invention will be described below withreference to FIGS. 21 to 28.

FIG. 21 shows the general configuration of an exposure apparatus 700according to an embodiment of the present invention. The exposureapparatus 700 is a scan-exposure apparatus of a step-and-scan type, thatis, a so-called scanning stepper. As will be described later, theexposure apparatus 700 of this embodiment includes a projection opticalsystem PL. In the following description: (a) the direction of theoptical axis AX of the projection optical system PL is designated aZ-axis direction; (b) the direction in which a reticle R serving as amask, and a wafer W serving as a substrate, are relatively scanned in aplane orthogonal to the Z-axis direction is designated a Y-axisdirection; and (c) the direction orthogonal to the Z-axis and Y-axisdirections is designated an X-axis direction. Additionally, the reticleand the wafer are generically referred to as “object”.

The exposure apparatus 700 includes an illumination system IOP, areticle stage RST serving as a mask stage for holding a reticle R, theprojection optical system PL, a wafer stage assembly 712 composed of awafer stage WST serving as a substrate stage for holding a wafer W and awafer driving unit 711 for two-dimensionally driving the wafer stage WSTin the X and Y directions, a control system for the devices, and thelike.

As disclosed in, for example, Japanese Laid-Open Patent ApplicationPublication Nos. 9-320956 and 4-196513 and U.S. Pat. No. 5,473,410corresponding thereto, the illumination system IOP includes alight-source unit, a shutter, a secondary light-source forming opticalsystem (optical integrator), a beam splitter, a light-collecting lenssystem, a reticle blind, an imaging lens system, and the like (all notshown). The IOP emits illumination light EL for exposure (hereinaftersimply referred to “exposure light”) serving as an exposure beam havinga substantially uniform illumination distribution. The exposure light ELilluminates a rectangular (or arcuate) illumination area IAR on areticle R at uniform illuminance. Used as the exposure light EL is, forexample, ultraviolet bright lines (g-rays and i-rays) from an extra-highpressure mercury lamp, or far-ultraviolet or vacuum ultraviolet lightsuch as KrF excimer laser light (with a wavelength of 248 nm), ArFexcimer laser light (with a wavelength of 193 nm), and F₂ laser light(with a wavelength of 157 nm).

The reticle stage RST is placed on a top plate 713 of a second column729B constituting a main column 710, which will be described later. Thetop plate 713 also functions as a reticle base. Hereinafter, the topplate 713 will also be referred to as a “reticle base 713”.

A reticle R is fixed on the reticle stage RST by, for example, vacuumsuction. In order to position the reticle R, the reticle stage RST iscapable of two-dimensional micromotion (in the X-axis direction, theY-axis direction orthogonal thereto, and the direction of rotation aboutthe Z-axis direction orthogonal to the XY plane) in a planeperpendicular to the Z-axis.

The reticle stage RST can also be moved on the reticle base 713 at adesignated scanning speed in a predetermined scanning direction (in theY-axis direction in this embodiment) by a reticle driving section (notshown) serving as a driving device having a linear motor and the like.The stroke of the reticle stage RST is set so that the entire surface ofthe reticle R can cross at least the optical axis of the illuminationsystem IOP.

A movable mirror 17 is fixed on the reticle stage RST so as to reflect alaser beam from a reticle laser interferometer (hereinafter referred toas a “reticle interferometer”) 715. The position of the reticle stageRST in a stage moving plane is constantly detected by the reticleinterferometer 715 with a resolution of, for example, approximately 0.5nm to 1 nm. In reality, and as is known in the art, a movable mirrorhaving a reflecting surface orthogonal to the scanning direction (Y-axisdirection) and a movable mirror having a reflecting surface orthogonalto the non-scanning direction (X-axis direction) are disposed on thereticle stage RST, and one reticle interferometer is disposed in thescanning direction and two reticle interferometers are disposed in thenon-scanning direction. In FIG. 21, the mirrors are represented by themovable mirror 717 and the interferometers are represented by thereticle interferometer 715.

Positional information (or speed information) about the reticle stageRST from the reticle interferometer 15 is sent to a main control system721 via a stage control system 719. The stage control system 719 drivesthe reticle stage RST via the reticle driving section (not shown) basedon the positional information about the reticle stage RST according todirections from the main control system 21.

A pair of reticle alignment systems (not shown) is placed above thereticle R. The reticle alignment systems each include anepi-illumination system for illuminating a mark to be detected withillumination light having the same wavelength as that of the exposurelight EL, and a reticle alignment microscope for picking up an image ofthe mark to be detected. The reticle alignment microscope includes animaging optical system and an image pickup device. The result of imagepickup by the reticle alignment microscope is supplied to the maincontrol system 721.

The above-described main column 710 includes a first column 729A placedon a floor F of a clean room via a plurality of vibration-isolatingunits 775, and the second column 729B placed on the first column 729A.

The first column 729A is composed of a plurality of column supports 723placed in line at the tops of the respective vibration-isolating units775, and a barrel surface plate 725 horizontally supported by the columnsupports 723. In this case, microvibrations to be transmitted from thefloor F to the main column 710 including the barrel surface plate 725are isolated by the vibration-isolating units 775 on the microgravitylevel.

The second column 729B is composed of a plurality of leg portions 727embedded in the upper surface of the first column 729A, and theabove-described top plate (reticle base) 713 horizontally supported bythe leg portions 727.

The projection optical system PL is inserted from above through anopening (not shown) formed in the center of the barrel surface plate725, and is supported by the barrel surface plate 725 via a flange (notshown) formed at about the center of a barrel thereof in the heightdirection. In this embodiment, the projection optical system PL is arefracting optical system that is formed of a double-sided telecentricreduction system composed of a plurality of lens elements arranged atpredetermined intervals along the optical-axis direction AX (the Z-axisdirection). The projection optical system PL may be a reduction systemthat is one-sided telecentric (for example, telecentric only on the sideof the wafer stage WST). The projection magnification of the projectionoptical system PL is set at, for example, ¼, ⅕, or ⅙. For this reason,when the illumination area IAR on the reticle R is illuminated withillumination light from the illumination optical system IOP, a reducedimage (partial inverted image) of a circuit pattern in the illuminationarea IAR of the reticle R is formed on an exposure area IA of a wafer Whaving a photoresist applied on its surface, which is conjugate with theillumination area IAR, via the projection optical system PL by theillumination light passed through the reticle R.

Adjacent to the projection optical system PL, an off-axis alignmentmicroscope ALG is placed. The alignment microscope ALG includes threetypes of alignment sensors, an LSA (Laser Step Alignment) type, an FIA(Field Image Alignment) type, and an LIA (Laser InterferometricAlignment) type, and can measure the positions in the X and Ytwo-dimensional directions of a fiducial mark on a fiducial mark plateand an alignment mark on the wafer.

In this embodiment, the three types of alignment sensors are useddepending on the operation, such as so-called search alignment fordetecting the positions of a predetermined number of search alignmentmarks on the wafer W so as to measure the general position of the waferW, and fine alignment for detecting the positions of a predeterminednumber of fine alignment marks on the wafer W so as to exactly measurethe positions of shot areas.

Digitized wave signals, which are obtained by converting informationfrom the alignment sensors constituting the alignment microscope ALGfrom analog to digital by an alignment control device (not shown), aresubjected to computation, and the mark positions are thereby detected.The detection result is transmitted to the main control system 721.

The exposure apparatus 700 of this embodiment further includes amultipoint focal position detecting system serving as one ofoblique-incidence type focus detecting systems for detecting thepositions of the exposure area IA and the adjacent area in the Z-axisdirection (the optical axis direction AX) on the wafer W. The multipointfocal position detecting system is composed of a light-emitting opticalsystem and a light-receiving optical system that are not shown, and hasa structure similar to that disclosed in, for example, JapaneseLaid-Open Patent Application Publication No. 6-283403 and U.S. Pat. No.5,448,332 corresponding thereto.

The above-described wafer stage assembly 712 is placed below theprojection optical system PL. The wafer stage assembly 712 is composedof the wafer stage WST for holding a wafer W and the wafer driving unit711 serving as a driving device.

A wafer W is fixed on the upper surface of the wafer stage WST via awafer holder (not shown) by electrostatic suction or vacuum suction. Afiducial mark plate FM is also fixed on the wafer stage WST. Thefiducial mark plate FM has various fiducial marks for base linemeasurement for measuring the distance from the center of detection ofthe alignment microscope ALG to the optical axis of the projectionoptical system PL.

On the upper surface of the wafer stage WST, as shown in FIG. 22, an Xmovable mirror 802X is disposed at one end in the X-axis direction (a+X-side end), and extends in the Y-axis direction, and a Y movablemirror 802Y is disposed at one end in the Y-axis direction (a −Y-sideend), and extends in the X-axis direction. The outer surfaces of themovable mirrors 802X and 802Y are mirror-finished reflecting surfaces.In FIG. 21, the movable mirrors 802X and 802Y are represented by amovable mirror 802.

An X-axis interferometer and a Y-axis interferometer (not shown) areplaced opposed to the reflecting surfaces of the movable mirrors 802Xand 802Y. Interferometric beams from the X-axis and Y-axisinterferometers are projected onto the reflecting surfaces of themovable mirrors 802X and 802Y, and the reflected beams from thereflecting surfaces are received by the respective interferometers. Theamounts of displacement of the reflecting surfaces of the movablemirrors from the reference positions are thereby measured, so that thetwo-dimensional position of the wafer stage WST is detected. In FIG. 21,the X-axis interferometer and the Y-axis interferometer are representedby a wafer interferometer 33.

The wafer driving unit 711 will now be described in detail withreference to FIGS. 22 to 27.

Referring to FIG. 22, the wafer driving unit 711 includes: (a) a Y-axislinear motor device (hereinafter referred to as a “Y-axis motor device”)YM serving as a first driving device (or as a second driving device) fordriving the wafer stage WST on a wafer surface plate 714 in the Y-axisdirection, and (b) a first X-axis linear motor device (hereinafterreferred to as a “first X-axis motor device”) XMA and a second X-axislinear motor device (hereinafter referred to as a “second X-axis motordevice”) XMB serving as a second driving device (or as a first drivingdevice) for moving the wafer stage WST and the Y-axis motor device YM onthe wafer surface plate 714 in the X-axis direction.

The first X-axis motor device XMA (more specifically, an X-axisstationary member 718A which will be described later) is supported in anon-contact manner by frames 716A1 and 716A2 fixed on the upper surfacesof two corners of a wafer base BS on the +Y-direction side so that it isrestrained in the Y-axis direction and the Z-axis direction. The secondX-axis motor device XMB (more specifically, an X-axis stationary member718B which will be described later) is similarly supported in anon-contact manner by frames 716B1 and 716B2 fixed on the upper surfacesof two corners of the wafer base BS on the −Y-direction side so that itis restrained in the Y-axis direction and the Z-axis direction.

The first X-axis motor device XMA includes the X-axis stationary member718A and an X-axis moving member 720A that moves in the X-axis directionalong the X-axis stationary member 718A in engagement therewith, asshown in FIG. 22 and in FIG. 23, which is a partially broken view of thewafer stage WST and a part of the wafer driving device shown in FIG. 22.

The X-axis stationary member 18A includes: (i) a magnetic pole unit726A1 of U-shaped YZ-plane cross section that extends in the X-axisdirection, (ii) a magnetic pole unit 726A2 disposed on the −Z side(lower side) of the magnetic pole unit 726A1 and having a structuresimilar to that of the magnetic pole unit 726A1, (iii) platelike X-axisguide members 728A1 and 728A2 respectively disposed on the −Y-sides ofthe magnetic pole units 726A1 and 726A2 so as to extend in the X-axisdirection, and (iv) holding members 730A1 and 730A2 for holding themagnetic pole units 726A1 and 726A2 and the X-axis guide members 728A1and 728A2 in a predetermined positional relationship.

As shown in FIG. 23, the magnetic pole unit 726A1 includes a yoke 732 ofU-shaped cross section, and a plurality of field magnets 734 arranged onthe upper and lower opposing surfaces of the yoke 732 at predeterminedintervals in the X-axis direction. Since the pole faces of the fieldmagnets 734 opposing in the Z-axis direction are opposite in polarity,Z-axis direction magnetic flux is mainly generated between the opposingfield magnets 734. Since the pole faces of the field magnets 734 thatare adjacent to each other in the X-axis direction are opposite inpolarity, an alternating magnetic field is formed in the X-axisdirection in a space inside the yoke 732.

The magnetic pole unit 726A2 has a structure similar to that of theabove-described magnetic pole unit 726A1.

As shown in FIG. 23, the holding member 30A1 includes: (i) a fixingmember 736A1 for fixing the magnetic pole units 726A1 and 726A2 and theX-axis guide members 728A1 and 728A2 in a predetermined positionalrelationship, and (ii) an upper face member 740A1 and a lower facemember 738A1 for clamping the fixing member 736A1 from both sides in theZ-axis direction (from above and below). An armature unit 742A1 composedof armature coils arranged at predetermined intervals in the X-axisdirection is embedded in the upper surface of the upper face member740A1, as shown in FIG. 23 and FIG. 24A, which is a cross-sectionalview, taken along line D—D in FIG. 22. An armature unit 742A2 similar tothe armature unit 742A1 is embedded in the lower surface of the lowerface member 738A1.

The other holding member 730A2 includes a fixing member 736A2, and anupper face member 740A2 and a lower face member 738A2 for clamping thefixing member 736A2 from above and below, as shown in FIG. 23.

The X-axis stationary member 718A with the above-described structure issupported in a non-contact manner by vacuum preload hydrostatic gasbearing devices (hereinafter simply referred to as “bearing devices” forconvenience) 99 disposed on the inner sides (both inner sides in theY-axis direction and both inner sides in the Z-axis direction) of theframes 716A1 and 716A2 shown in FIG. 22 (see FIG. 24A; the bearingdevices disposed in the frame 716A2 are not shown). That is, while theX-axis stationary member 718A is restrained in the Y-axis direction andthe Z-axis direction, it is not restrained at all in the X-axisdirection. Therefore, when force in the X-axis direction acts on theX-axis stationary member 718A, the X-axis stationary member 718A movesin the X-axis direction in response to this force.

The X-axis stationary member 718A is substantially symmetric in thevertical direction with respect to its center in the Z-axis direction,as shown in FIG. 27 as a YZ cross-sectional view of the wafer stageassembly 712. For this reason, the center of gravity of the X-axisstationary member 718A in the Z-axis direction lies at a point A₁.

The X-axis moving member 20A includes, as generally shown in FIGS. 22and 23: (a) a slide member 746A, (b) a frame member 748A, and (c)armature units 750A1 and 750A2. The slide member 746A is formed of aflat plate having a +Y-side face opposing the X-axis guide members 728A1and 728A2. The frame member 748A has a rectangular cross section that isdisposed at about the center of the +Y-side face of the slide member746A in a space between the magnetic pole units 726A1 and 726A2 so as toextend toward the +Y side. The armature units 750A1 and 750A2 aredisposed at a nearly equal distance from the frame member 748A in the±Z-axis direction (at the positions corresponding to the inner spaces ofthe magnetic pole units 726A1 and 726A2) and have therein a plurality ofarmature coils arranged at predetermined intervals in the X-axisdirection.

The −Y-side face of the slide member 746A is provided with a bearingdevice 754A (see FIG. 27), similar to a bearing device 754B of a slidemember 746B, constituting an X-axis moving member 720B of the secondX-axis motor device XMB which will be described later with reference toFIG. 23. The X-axis moving member 720A is supported in no contact withthe X-axis stationary member 718A with a clearance of approximatelyseveral micrometers therebetween in the Y-axis direction by staticpressure of compressed gas (for example, helium or gaseous nitrogen (orclean air)) jetted from the bearing device 754A onto the X-axis guidemembers 728A1 and 728A2 constituting the above-described X-axisstationary member 718A.

Similar bearing devices 752A1 and 752A2 are also disposed on the upperand lower surfaces of the frame member 748A (the bearing device 752A2 isnot shown in FIG. 23, but is shown in FIG. 27). The X-axis moving member720A is supported in no contact with the X-axis stationary member 718Awith a clearance of approximately several micrometers therebetween inthe Z-axis direction by static pressure of compressed gas jetted fromthe bearing devices 752A1 and 752A2 onto the lower surface of themagnetic pole unit 726A1 and the upper surface of the magnetic pole unit726A2 constituting the X-axis stationary member 718A.

At the center of the slide member 746A, an opening 756A (see FIG. 27) isformed so as to be similar to an opening 756B formed in the slide member746B constituting the X-axis moving member 720B of the second X-axismotor device XMB shown in FIG. 23, which will be described later. Theopening 756A communicates with a cavity 780A of the frame member 748A.

Since the X-axis moving member 720A is substantially symmetric in thevertical direction with respect to its center in the Z-axis direction,as shown in FIG. 27, the position in the Y-axis direction and the Z-axisdirection of a center of gravity A₂ thereof coincides with that of thecenter of gravity A₁ of the X-axis stationary member 718A.

In the first X-axis motor device XMA with the above-described structure,the X-axis moving member 720A is moved along the X-axis guide members728A1 and 728A2 in the X-axis direction by Lorentz force produced by anelectromagnetic interaction between the current passing through thearmature coils of the armature units 750A1 and 750A2 and a magneticfield generated by the field magnets of the magnetic pole units 726A1and 726A2 of the X-axis stationary member 718A. In this case, theposition of the driving force (point of action of the driving force)acting on the X-axis moving member 720A in the X-axis directioncoincides with the position of the center of gravity A₂ of the X-axismoving member 720A. The position in the Y-axis direction and the Z-axisdirection of the reaction force (point of action of the reaction force)acting on the X-axis stationary member 718A in the X-axis direction inconnection with the driving of the X-axis moving member 720A coincideswith the position in the Y-axis direction and the Z-axis direction ofthe center of gravity A₁ of the X-axis stationary member 718A.

The amount and direction of driving force in the X-axis direction actingon the X-axis moving member 720A are controlled by the waveform(amplitude and phase) of current supplied from the main control system721 to the armature coils of the armature units 750A1 and 750A2 via thestage control system 719.

Refrigerant (coolant) is supplied to the armature units 750A1 and 750A2so as to cool the armature coils. The flow rate of the refrigerant isalso controlled by the main control system 721.

The second X-axis motor device XMB is placed in rotational symmetry tothe above-described first X-axis motor device XMA, as shown in FIG. 22,and is similarly constructed. That is, the second X-axis motor deviceXMB includes an X-axis stationary member 718B having a structure similarto that of the X-axis stationary member 718A of the first X-axis motordevice XMA, and an X-axis moving member 720B having a structure similarto that of the X-axis moving member 720A.

The X-axis stationary member 718B includes: (i) magnetic pole units726B1 and 726B2 similar to the above magnetic pole units 726A1 and726A2, (ii) X-axis guide members 728B1 and 728B2 similar to the aboveX-axis guide members 728A1 and 728A2, and (iii) holding members 730B1and 730B2 for holding the magnetic pole units 726B1 and 726B2 and theX-axis guide members 728B1 and 728B2 in a predetermined positionalrelationship.

The holding member 730B1 disposed at the +X-side end of the X-axisstationary member 718B includes: (i) a fixing member 736B1 similar tothe above fixing member 736A1, and (ii) an upper face member 740B1 and alower face member 738B1 for clamping the fixing member 736B1 from bothsides in the Z-axis direction (from above and below). An armature unit742B1 similar to the above armature unit 742A1 is embedded in the uppersurface of the upper face member 740B1, and an armature unit 742B2similar to the above armature unit 742A2 (see FIG. 24) is embedded inthe lower surface of the lower face member 738B1.

The holding member 730B2 opposing the holding member 730B1 in the X-axisdirection has a structure similar to that of the above holding member730A2. That is, the holding member 730B2 includes a fixing member 736B2,and an upper face member 740B2 and a lower face member 738B2 forclamping the fixing member 736B2 from above and below.

Since the X-axis stationary member 718B has the above-describedstructure, the position in the Z-axis direction of its center of gravityB₁ coincides with the position in the Z-axis direction of the center ofgravity A₁ of the X-axis stationary member 718A.

The frames 716B1 and 716B2 are provided, on their inner sides, withbearing devices 799 in a manner similar to that of the frames 716A1 and716A2 (see FIG. 24B).

As shown in FIG. 23, the X-axis moving member 720B includes: (a) a slidemember 746B having a structure similar to that of the slide member 746A,(b) a frame member 748B disposed at about the center of the −Y-side faceof the slide member 746B and having a structure similar to that of theframe member 748A, and (c) armature units 750B1 and 750B2 disposed at anearly equal distance from the frame member 748B in the ±Z direction andhaving a structure similar to that of the armature units 750A1 and750A2.

The +Y-side face of the slide member 746B is provided with a bearingdevice 754B, and the upper and lower faces of the frame member 748B areprovided with bearing devices 752B1 and 752B2 (not shown in FIG. 23, butshown in FIG. 27) similar to the above bearing devices 752A1 and 752A2.

An opening 756B is formed in the center of the slide member 746B, asshown in FIG. 23. The opening 756B communicates with a cavity 780B ofthe frame member 748B (see FIG. 27).

The position in the Y-axis direction and the Z-axis direction of thecenter of gravity B₂ of the X-axis moving member 720B with theabove-described structure coincides with the position in the Y-axisdirection and the Z-axis direction of the center of gravity B₁ of theX-axis stationary member 718B, as shown in FIG. 27.

In the second X-axis motor device XMB, in a manner similar to that ofthe first X-axis motor device XMA, the X-axis moving member 720B ismoved along the X-axis guide members 728B1 and 728B2 in the X-axisdirection by Lorentz force produced by an electromagnetic interactionbetween current passing through the armature coils of the armature units750B1 and 750B2 and a magnetic field generated by the field magnets ofthe magnetic pole units 726B1 and 726B2 of the X-axis stationary member718B. In this case, the position of the driving force (point of actionof the driving force) acting on the X-axis moving member 720B in theX-axis direction coincides with the position of the center of gravity B₂of the X-axis moving member 720B. The position in the Y-axis directionand the Z-axis direction of the reaction force (point of action of thereaction force) acting on the X-axis stationary member 718B in theX-axis direction in connection with the driving of the X-axis movingmember 720B coincides with the position in the Y-axis direction and theZ-axis direction of the center of gravity B of the X-axis stationarymember 718B.

In a manner similar to that of the first X-axis motor device XMA, theamount and direction of driving force in the X-axis direction acting onthe X-axis moving member 720B are controlled by the waveform (amplitudeand phase) of current supplied from the main control system 721 to thearmature coils of the armature units 750B1 and 750B2 via the stagecontrol system 719.

Refrigerant is supplied to the armature units 750B1 and 750B2constituting the second X-axis motor device XMB so as to cool thearmature coils, in a manner similar to that of the above armature units750A1 and 750A2. The flow rate of the refrigerant is also controlled bythe main control system 721.

In the frame 716A1 corresponding to the holding member 730A1, as shownin FIG. 24A, magnetic pole units 744A1 and 744A2, each composed of amagnetic material and a plurality of field magnets arranged atpredetermined intervals in the X-axis direction, are disposed at thepositions corresponding to the armature units 742A1 and 742A2 of theupper face member 740A1 and the lower face member 738A1 (that is, in theupper and lower opposing faces of the frame 716A1). In the magnetic poleunits 744A1 and 744A2, pole faces of the field magnets adjacent to eachother in the X-axis direction are opposite in polarity.

In the frame 716B1 corresponding to the holding member 730B1, as shownin FIG. 24B, which is a view of the holding member 730B1 and the frame716B1, as viewed from the +X-axis direction, magnetic pole units 744B1and 744B2, each composed of a magnetic material and a plurality of fieldmagnets arranged at predetermined intervals in the X-axis direction, aredisposed at the positions corresponding to the armature units 742B1 and742B2 of the upper face member 740B1 and the lower face member 738B1(that is, in the upper and lower opposing faces of the frame 716B1). Inthe magnetic pole units 744B1 and 744B2, pole faces of the field magnetsadjacent to each other in the X-axis direction are opposite in polarity.

For this reason, an alternating magnetic field is formed in the X-axisdirection in a space where the armature units 742A1 and 742A2 are placedopposed to the magnetic pole units 744A1 and 744A2. A periodic magneticfield also is formed in the X-axis direction in a space where thearmature units 742B1 and 742B2 are placed opposed to the magnetic poleunits 744B1 and 744B2.

As a result, the armature unit 742A1 serving as a moving member and themagnetic pole unit 744A1 serving as a stationary member constitute alinear motor 745A1, and the armature unit 742A2 serving as a movingmember and the magnetic pole unit 744A2 serving as a stationary memberconstitute a linear motor 745A2, as shown in FIG. 24A. The armature unit742B1 serving as a moving member and the magnetic pole unit 744B1serving as a stationary member constitute a linear motor 745B1, and thearmature unit 742B2 serving as a moving member and the magnetic poleunit 744B2 serving as a stationary member constitute a linear motor745B2, as shown in FIG. 24B. The linear motors 745A1, 745A2, 745B1, and745B2 generate driving force by an electromagnetic interaction.

The linear motors 745A1 and 745A2 constitute a first X-positioncorrection device, which will be described later, and the linear motors745B1 and 745B2 constitute a second X-position correction device. Theposition in the Y-axis direction and the Z-axis direction of the drivingforce in the X-axis direction applied from the first X-positioncorrection device to the X-axis stationary member 718A coincides withthe position in the Y-axis direction and the Z-axis direction of thecenter of gravity A₁ of the X-axis stationary member 718A shown in FIG.27. The position in the Y-axis direction and the Z-axis direction of thedriving force in the X-axis direction applied from the second X-positioncorrection device to the X-axis stationary member 718B coincides withthe position in the Y-axis direction and the Z-axis direction of thecenter of gravity B₁ of the X-axis stationary member 718B.

The amount and direction of driving force in the X-axis directionapplied from the first and second X-position correction devices actingon the X-axis stationary members 718A and 718B are controlled bycontrolling the waveform (amplitude and phase) of current supplied fromthe main control system 721 to the armature coils of the armature units742A1, 742A2, 742B1, and 742B2 via the stage control system 719.

Referring again to FIG. 22, the Y-axis motor device YM includes a Y-axisstationary member 722 and a Y-axis moving member 770.

The Y-axis stationary member 722 includes, as shown in FIG. 25: (a) anarmature unit 758 having therein a plurality of armature coils arrangedat predetermined intervals in the Y-axis direction and extending in theY-axis direction, (b) a housing member 759 for supporting and housingthe armature unit 758, and (c) a pair of Y-axis guide members 763 and764 disposed on both sides in the X-axis direction of the housing member759. On the +Y-direction side, the armature coils are arranged adjacentto the +Y-side ends of the Y-axis guide members 763 and 764. Incontrast, on the −Y-direction side, the ends of the Y-axis guide members763 and 764 protrude in the −Y direction.

As shown in FIG. 25, the Y-axis guide member 763 has iron plate holdingportions 762A1 and 762B1 on the −X-side faces at both ends in thelongitudinal direction, and the Y-axis guide member 764 has iron plateholding portions 762A2 and 762B2 on the +X-side faces at both ends inthe longitudinal direction. Iron plates 760A1, 760B1, 760A2, and 760B2(the iron plate 760B2 in the iron plate holding portion 762B2 is notshown in FIG. 25, but is shown in FIG. 26) are embedded in the ironplate holding portions 762A1, 762B1, 762A2, and 762B2.

Both ends in the longitudinal direction of the Y-axis stationary member722 are, as shown in FIG. 23, inserted in the frame members 748A and748B via the openings 756A and 756B formed in the slide members 746A and746B of the above-described X-axis moving members 720A and 720B.

FIG. 26 is a partly omitted cross-sectional view of the Y-axis motordevice YM and the X-axis moving members 720A and 720B, taken along anX-Y plane slightly above the center in the height direction. As shown inFIG. 26, electromagnets 790A1, 790A2, 790B1, and 790B2 are fixed on theinner side walls of the frame members 748A and 748B in the X-axis movingmembers 720A and 720B. The electromagnets 790A1, 790A2, 790B1, and 790B2are respectively opposed to the iron plates 760A1, 760A2, 760B1, and760B2 embedded in the Y-axis ends of the Y-axis stationary member 722.The Y-axis stationary member 722 is restrained in the X-axis directionin a non-contact manner by magnetic force produced between the ironplates 760A1, 760A2, 760B1, and 760B2 and the electromagnets 790A1,790A2, 790B1, and 790B2. On the other hand, since the Y-axis stationarymember 722 is not restrained at all in the Y-axis direction, it can bemoved in the Y-axis direction in response to force applied in the Y-axisdirection. The iron plates 760A1, 760A2, 760B1, and 760B2 and theelectromagnets 790A1, 790A2, 790B1, and 790B2 constitute an X-axisrestraint mechanism for the Y-axis stationary member 722.

In the X-axis restraint mechanism, magnetic force between each of theelectromagnets 790A1, 790A2, 790B1, and 790B2 and a corresponding ironplate is controlled by controlling current supplied to the electromagnetvia the stage control system 719 by the main control system 721.

Such control of magnetic force between the iron plates 760A1, 760A2,760B1, and 760B2 and the corresponding electromagnets 790A1, 790A2,790B1, and 790B2 in the X-axis restraint mechanism allows the Y-axisstationary member 722 and the wafer W (the wafer stage WST) to beslightly driven in a direction θ_(Z).

As shown in FIG. 25, placed inside the frame member 748A are: (i) amagnet 792A1 composed of a plurality of field magnets arranged atpredetermined intervals in the Y-axis direction so as to be opposed tothe upper surface of the armature unit 758, and (ii) a magnet 792A2 (notshown in FIG. 25, but shown in FIG. 27) composed of a plurality of fieldmagnets arranged at predetermined intervals in the Y-axis direction soas to be opposed to the lower surface of the armature unit 758. The polefaces of the opposing field magnets in the magnets 792A1 and 792A2 areopposite in polarity. As a result, the armature unit 758 and a magneticpole unit composed of the magnets 792A1 and 792A2 constitute a linearmotor for driving the Y-axis stationary member 722 in the Y-axisdirection.

The linear motor constitutes a Y-axis position correction device whichwill be described later. The position in the X-axis direction and theZ-axis direction of the driving force in the Y-axis direction to begiven from the Y-axis position correction device to the Y-axisstationary member 722 coincides with the position in the X-axisdirection and the Z-axis direction of a center of gravity C₁ of theY-axis stationary member 722 shown in FIG. 27. The amount and directionof driving force in the Y-axis direction applied from the Y-axisposition correction device and acting on the Y-axis stationary member722 are controlled by controlling the waveform (amplitude and phase) ofcurrent supplied from the main control system 721 to the armature coils,which constitute a part of the armature unit 758 held between themagnets 792A1 and 792A2, via the stage control system 719.

Below and adjacent to both ends in the Y-axis direction of the Y-axisguide members 763 and 764, as shown in FIG. 27, floating members 782Aand 782B are placed. The floating members 782A and 782B have, at theirbottoms, bearing devices 755A and 755B for maintaining a clearance fromthe wafer surface plate 714. The floating members 782A and 782B and theY-axis stationary member 722 are supportingly floated at a distance ofapproximately several micrometers from the wafer surface plate 714 bystatic pressure of compressed gas jetted from the bearing devices 755Aand 755B onto the upper surface of the wafer surface plate 714.

In the Y-axis stationary member 722, the armature unit 758 is fixed tothe portions of the Y-axis guide members 763 and 764 slightly offsetdownward from the center in the Z-axis direction, as is evident from thepositional relationship between the armature unit 758 and the Y-axisguide member 764 which is representatively shown in FIG. 27. Theposition in the Z-axis direction of the center of gravity C₁ of theY-axis stationary member 722 coincides with the position in the Z-axisdirection of the center of gravity A₁ of the X-axis stationary member718A described above.

Referring again to FIG. 25, the Y-axis moving member 770 includes: (a) amagnet holding member 778 having a rectangular XZ cross section shape,(b) a magnetic pole unit 772A placed on the upper inner surface of themagnet holding member 778 and having field magnets arranged atpredetermined intervals in the Y-axis direction and a magnetic pole unit772B (not shown in FIG. 25, but shown in FIG. 27) placed on the lowerinner surface of the magnet holding member 778 and having field magnetsarranged at predetermined intervals in the Y-axis direction, (c) a topplate 784 placed on the magnet holding member 778 so as to be nearlysquare in plan view, and (d) a center of gravity adjusting member 786placed under the magnet holding member 778. The above-described Y-axisstationary member 722 is passed through the inner space of the magnetholding member 778.

The magnetic pole unit 772A is, as shown in FIG. 27, composed of: (i) amagnetic member 781A fixed on the upper inner surface of the magnetholding member 778, and (ii) a plurality of field magnets 783A arrangedon the lower surface of the magnetic member 781A at predeterminedintervals in the Y-axis direction. In this case, pole faces of the fieldmagnets 783A face the upper surface of the armature unit 758. The polefaces of the field magnets 783A adjacent to each other in the Y-axisdirection are opposite in polarity.

The magnetic pole unit 772B is composed of: (i) a magnetic member 781Bfixed on the lower inner surface of the magnet holding member 778, and(ii) a plurality of field magnets 783B arranged on the upper surface ofthe magnetic member 781B at predetermined intervals in the Y-axisdirection. In this case, pole faces of the field magnets 783B face thelower surface of the armature unit 758. The pole faces of the fieldmagnets 783B adjacent to each other in the Y-axis direction are oppositein polarity.

The pole faces of the above-described field magnets 783A and 783Bopposing in the Z-axis direction are opposite in polarity. For thisreason, magnetic flux in the Z-axis direction is mainly produced betweenthe opposing field magnets 783A and 783B. Since the pole faces of thefield magnets 783A and 783B that are adjacent to each other in theY-axis direction are opposite in polarity, as described above, analternating magnetic field is formed in the Y-axis direction in a spacebetween the field magnets 783A and 783B.

A plurality of bearing devices 794 are arranged on the bottom surface ofthe center of gravity position adjusting member 786. The Y-axis movingmember 770 is supportingly floated at a distance of approximatelyseveral micrometers from the wafer surface plate 714 by static pressureof compressed gas jetted from the bearing devices 794 onto the uppersurface of the wafer surface plate 714. Similarly, bearing devices (notshown) are provided on the inner faces of the magnet holding member 778opposing in the X-axis direction, and the Y-axis moving member 770 isheld in no contact with (i.e., spaced from) the outer surfaces of theY-axis guide members 763 and 764 constituting the Y-axis stationarymember 722 at a distance of approximately several micrometers therefrom.By keeping the distance fixed, the Y-axis moving member 770 and thewafer stage WST, which will be described later, are prevented fromrotating (yawing) in θ_(Z) when the Y-axis moving member 770 is drivenin the Y-axis direction by the Y-axis linear motor.

The pressure and flow rate of compressed gas to be jetted from thebearing devices 794 of the Y-axis moving member 770 are controlled bythe stage control system 719 shown in FIG. 21 according to instructionsfrom the main control system 721. The other bearing devices describedabove are also controlled in a similar manner.

As shown in FIG. 27, a Z-tilt driving mechanism 776 is placed on theupper surface of the Y-axis moving member 770 so as to control theZ-axis position and attitude (tilt) of the wafer stage WST.

The Z-tilt driving mechanism 776 is composed of three voice coil motors(not shown) that are placed at the positions on the upper surface of thetop plate 784 of the Y-axis moving member 770 corresponding to thevertexes of a nearly equilateral triangle so as to support andindependently and slightly drive the wafer stage WST in the Z-axisdirection. Therefore, the wafer stage WST is slightly driven by theZ-tilt driving mechanism 776 in three degree-of-freedom directions, theZ-axis direction, the θ_(X) direction (direction of rotation about theX-axis), and the θ_(Y) direction (direction of rotation about theY-axis). Driving of the Z-tilt driving mechanism 776 is controlled bythe stage control system 719 according to instructions from the maincontrol system 721.

Since the Y-axis moving member 770 has the structure described above,the position in the X-axis direction and the Z-axis direction of acenter of gravity C₂ of a composite of the Y-axis moving member 770 andthe wafer stage WST coincides with the position in the X-axis directionand the Z-axis direction of the center of gravity C₁ of the Y-axisstationary member 722, as shown in FIG. 27.

In the Y-axis motor device YM with the above-described structure, theY-axis moving member 770 is moved along the Y-axis guide members 763 and764 in the Y-axis direction by Lorentz force produced by anelectromagnetic interaction between current passing through the armaturecoils of the armature unit 758 and a magnetic field generated by thefield magnets 783A and 783B of the magnetic pole units 772A and 772B ofthe Y-axis stationary member 722. In this case, the position of thedriving force (point of action of the driving force) in the Y-axisdirection acting on the Y-axis moving member 770 coincides with theposition of the center of gravity C₂ of the Y-axis moving member 770.The position in the Y-axis direction and the Z-axis direction of thereaction force (point of action of the reaction force) in the Y-axisdirection acting on the Y-axis stationary member 722 in connection withdriving of the Y-axis moving member 770 coincides with the position inthe X-axis direction and the Z-axis direction of the center of gravityC₁ of the Y-axis stationary member 722.

The amount and direction of driving force in the Y-axis direction actingon the Y-axis moving member 770 are controlled by controlling thewaveform (amplitude and phase) of current supplied from the main controlsystem 721 to the armature coils of the armature unit 758 via the stagecontrol system 719.

Refrigerant for cooling the armature coils is supplied to the armatureunit 758. The flow rate of the refrigerant is also controlled by themain control system 721.

An exposure operation by the exposure apparatus 700 of this embodimentwith the above structure will now be described. Exposure for second andsubsequent layers of a wafer W will be described as an example.

First, a reticle R is loaded onto the reticle stage RST by a reticleloader (not shown). Subsequently, reticle alignment and base linemeasurement are performed. During the reticle alignment and the baseline measurement, the main control system 721 controls the wafer drivingunit 711 via the stage control system 719 so as to move the wafer stageWST two-dimensionally. For the purpose of such two-dimensional movementof the wafer stage WST, the main control system 721 controls thewaveform of current supplied to the armature units 750A1, 750A2, 750B1,and 750B2 for X-axis driving in the first and second X-axis motordevices XMA and XMB of the wafer driving unit 711 and the waveform ofcurrent supplied to the armature coils of the armature unit 758 of theY-axis motor device YM, based on positional information (or speedinformation) about the wafer stage WST from the wafer interferometer733. When driving the wafer stage WST in the X-axis direction, currentis controlled so that driving forces given from the first and secondX-axis motor devices XMA and XMB to the X-axis moving members 720A and720B are equal in amount and direction.

In this case, since the X-axis moving members 720A and 720B arerestrained in a non-contact manner in the Y-axis direction and theZ-axis direction, as described above, they are stably driven by thefirst and second X-axis motor devices XMA and XMB. Furthermore, sincethe centers of gravity A₂ and B₂ of the X-axis moving members 720A and720B coincide with the driving forces acting on the X-axis movingmembers 720A and 720B, no torque is produced in the X-axis movingmembers 720A and 720B, and all the driving forces are translational inthe X-axis direction. This allows the X-axis moving members 720A and720B to be driven in the X-axis direction with high efficiency.

Since the Y-axis moving member 770 is restrained in a non-contact mannerin the X-axis direction and the Z-axis direction, as described above, itis stably driven by the Y-axis motor device YM. Furthermore, since thecenter of gravity C₂ of the Y-axis moving member 770 and the drivingforce acting thereon coincide with each other, no torque is produced inthe Y-axis moving member 770, and all the driving force is translationalin the Y-axis direction. This allows the Y-axis moving member 770 to bedriven in the Y-axis direction with high efficiency.

When the X-axis moving members 720A and 720B are driven by the first andsecond X-axis motor devices XMA and XMB, reaction force in a directionopposite from the driving direction of the X-axis moving members 720Aand 720B is produced in the X-axis stationary members 718A and 718B. Inthis case, since the X-axis stationary members 718A and 718B arerestrained in a non-contact manner in the Y-axis direction and theZ-axis direction, they are moved in the X-axis direction opposite fromthe driving direction of the X-axis moving members 720A and 720B inresponse to the reaction force according to the law of conservation ofmomentum. As a result, most of the reaction force acting on the X-axisstationary members 718A and 718B is absorbed (by their movement), ratherthan being transmitted to wafer surface plate 714. Consequently, it ispossible to substantially completely prevent vibration from beinggenerated due to the reaction force produced when the X-axis movingmembers 720A and 720B are driven.

The main control system 721 controls the waveform of current supplied tothe armature coils of the armature units 742A1, 742A2, 742B1, and 742B2for X-axis driving in the first and second X-axis position correctiondevices via the stage control system 719. By such control, the first andsecond X-axis position correction devices drive the X-axis stationarymembers 718A and 718B in the X-axis direction at an appropriate time sothat the X-axis stationary members 718A and 718B are maintained withintheir stroke ranges even after being subsequently moved in the X-axisdirection due to the reaction force produced by driving of the X-axismoving members 720A and 720B.

When the Y-axis moving member 770 is driven by the Y-axis motor deviceYM, reaction force in a direction opposite from the driving direction ofthe Y-axis moving member 770 is produced in the Y-axis stationary member722. In this case, since the Y-axis stationary member 722 is restrainedin a non-contact manner in the X-axis direction and the Z-axisdirection, it is moved in the Y-axis direction opposite from the drivingdirection of the Y-axis moving member 770 in response to the reactionforce according to the law of conservation of momentum. As a result,most of the reaction force acting on the Y-axis stationary member 722 isabsorbed. Consequently, it is possible to substantially completelyprevent vibration from being generated due to the reaction forceproduced when the Y-axis moving member 770 is driven.

The main control system 721 controls the waveform of current supplied tothe armature coils of the armature unit 758 for Y-axis driving in theY-axis position correction device via the stage control system 719. Bysuch control, the Y-axis position correction device drives the Y-axisstationary member 722 in the Y-axis direction at an appropriate time sothat the Y-axis stationary member 722 is maintained within its strokerange even after being subsequently moved in the Y-axis direction due tothe reaction force produced by driving of the Y-axis moving member 770.

Under such control of the wafer driving unit 711 by the main controlsystem 721, reticle alignment and base line measurement are performedwhile moving the wafer stage WST. When the reticle alignment and baseline measurement are completed, a wafer W is loaded onto the wafer stageWST by a wafer loader (not shown). The wafer stage WST is moved to aloading position in order for the wafer W to be loaded thereon. Themovement of the wafer stage WST is controlled in a manner similar tothat of the above reticle alignment.

As shown in FIG. 28, a plurality of shot areas SA_(ij) serving as areasto be exposed are arranged in a matrix on the loaded wafer W. Each ofthe shot areas SA_(ij) has a chip pattern formed by exposure anddevelopment processes performed for the preceding layer, and a finealignment mark for fine alignment.

Subsequently, fine alignment is performed by, e.g., Enhanced GlobalAlignment (EGA) in which the array coordinates of the shot areas SA_(ij)on the wafer W are found by statistical calculation such as a leastsquares method. In the fine alignment process, the wafer stage WST ismoved so that a predetermined fine alignment mark is placed in anobservation area of an alignment microscope ALG when observing the finealignment mark. The movement of the wafer stage WST is controlled in amanner similar to that of the above-described reticle alignment. Finealignment by EGA is disclosed in, for example, Japanese Laid-Open PatentApplication No. 61-44429 and U.S. Pat. No. 4,780,617 correspondingthereto.

Subsequently, exposure is effected on each shot area on the wafer W by astep-and-scan method. The shot areas SA_(ij) are exposed in the orderillustrated in FIG. 28, that is, sequentially from a shot area SA_(1,1)in the row direction (+X direction). When exposure of the last shot areaSA_(1,7) of the first row is completed, exposure is then effected fromthe first SA_(2,9) of the second row in a row direction (−X direction)opposite from the direction of the first row. Subsequently, exposure issequentially effected to the last shot area while reversing thedirection of exposure at every linefeed.

Solid arrows in FIG. 28 show the direction of scanning for exposureareas IA in the shot areas of the wafer W. That is, this embodimentadopts a so-called alternate scanning method in which the scanningdirection is sequentially reversed as exposure progresses. As theexposure of the shot areas progresses, in fact, the wafer W is moved ina direction opposite from the direction shown by the solid arrows(including dotted lines) in FIG. 28.

In such an exposure process, the main control system 721 first controlsthe wafer driving unit 711 via the stage control system 719 based on theresult of the above fine alignment and positional information (or speedinformation) from the wafer interferometer 733, thereby moving the waferstage WST so as to place the wafer W into a start position ofscan-exposure for the first shot area SA_(1,1) on the wafer W. While themovement of the wafer stage WST in this case is also controlled in amanner substantially similar to that of the above reticle alignment,there are three differences as follows:

-   -   (1) At the scanning start position for the first shot area        SA_(1,1), the wafer W has a velocity component only in the −Y        direction, and the velocity component is set at a predetermined        value V_(W).    -   (2) At the scanning start position for the first shot area        SA_(1,1), the X-axis stationary members 718A and 718B are placed        in predetermined X-axis positions by the first and second X-axis        position correction devices. The predetermined X-axis positions        are set so as to ensure that there is sufficient space for the        stroke of (i.e., the movement of) the X-axis stationary member        718A when it is moved in the +X-axis direction by reaction force        produced when the wafer stage WST is moved in the −X-axis        direction by a distance corresponding to one shot area of the        wafer W (a distance X₁ shown in FIG. 28).    -   (3) At the scanning start position for the first shot area        SA_(1,1), the Y-axis stationary member 722 is placed in a        predetermined Y-axis position by the Y-axis position correction        device. The predetermined Y-axis position is set so as to ensure        that there is sufficient space for the stroke (i.e., the        movement) of the Y-axis stationary member 722 when it is moved        in the +Y-axis direction by reaction force produced by the        movement of the wafer stage WST during scan-exposure of the        first shot area SA_(1,1) (by a distance S shown in FIG. 28) and        the stepping movement thereof in the −Y-axis direction from the        first shot area SA_(1,1) to the second shot area SA_(1,2) (by a        distance Y₁ shown in FIG. 28) and to ensure that there is        sufficient space for the stroke of the Y-axis stationary member        722 when it is moved in the −Y-axis direction by reaction force        produced by the stepping movement of the wafer stage WST in the        +Y-axis direction from the second shot area SA_(1,2) to the        third shot area SA_(1,3) (by a distance Y₂ shown in FIG. 28).

Subsequently, the stage control system 719 starts relative movement inthe Y-axis direction between the reticle R and the wafer W, that is,between the reticle stage RST and the wafer stage WST, according todirections from the main control system 721. When both the stages RSTand WST reach their respective target scanning speeds and are broughtinto a constant-speed synchronous state, a pattern area of the reticle Rstarts to be illuminated with illumination light from the illuminationoptical system IOP, and scan-exposure is started. The above-describedrelative scanning is performed by controlling the reticle driving unit(not shown) and the wafer driving unit 711 by the stage control system719 while monitoring the values measured by the wafer interferometer 733and the reticle interferometer 715 described above.

The stage control system 719 synchronously controls the reticle stageRST and the wafer stage WST via the reticle driving unit and the waferdriving unit 711. In this case, in particular, during theabove-described scan-exposure, synchronous control is executed so thatthe ratio of the moving velocity V_(R) of the reticle stage RST in theY-axis direction and the moving velocity V_(W) of the wafer stage WST inthe Y-axis direction is maintained in accordance with the projectionmagnification (¼× or ⅕×) of the projection optical system PL.

Different pattern areas on the reticle R are sequentially illuminatedwith light. When illumination of all the pattern areas is completed,scan-exposure of the first shot area SA_(1,1) on the wafer W isterminated. The pattern areas (i.e., the pattern) on the reticle R arethereby reduced and transferred onto the first shot area SA_(1,1) viathe projection optical system PL. After the completion of scan-exposure,illumination of the pattern areas of the reticle R with the illuminationlight is terminated.

In the above-described synchronous movement for scan-exposure, the waferstage WST (and the wafer W) is moved by driving the Y-axis moving member770 by the Y-axis motor device YM in the wafer driving unit 711. Duringthe synchronous movement, the Y-axis position of the Y-axis stationarymember 722 is not corrected by the Y-axis position correction device.For this reason, reaction force produced by the driving of the Y-axismoving member 770 functions as a driving force for the Y-axis stationarymember 722, which is completely freely movable according to the law ofconservation of momentum, and thereby the reaction force is absorbed. Asa result, it is possible to substantially completely prevent vibrationdue to driving of the Y-axis moving member 770 by the Y-axis motordevice YM.

During the synchronous movement, of course, the driving of the waferstage WST in the θ_(Z) direction by the X-axis restraint device, and thedriving of the wafer stage WST in the Z-axis direction, the θ_(X)direction, and the θ_(Y) direction by the Z-tilt driving mechanism 776are appropriately performed. Since the X-axis restraint device and theZ-tilt driving mechanism 776 have the structures described above, nosignificant variation occurs due to the driving.

When the above-described scan-exposure of the first shot area SA_(1,1)is completed, the stage control system 719 controls the wafer drivingunit 711 so that the wafer stage WST is moved in a stepping manner toplace the wafer W into the scanning start position of the next shot area(herein, the second shot area SA_(1,2)). Such stepping movement of thewafer W is made so as to satisfy the initial conditions of the positionand speed at the completion of scan-exposure of the first shot areaSA_(1,1) and the following two at-end conditions:

-   -   (1′) At the scan-exposure starting position of the second shot        area SA_(1,2), the wafer W has a velocity component only in the        +Y direction, and the velocity component is set at the        predetermined value V_(W).    -   (2′) At the scan-exposure starting position of the second shot        area SA_(1,2), the X-axis stationary members 718A and 718B are        placed into predetermined X-axis positions by the first and        second X-axis position correction devices. The predetermined        X-axis positions are set so as to ensure that there is        sufficient room for the stroke of the X-axis stationary members        718A and 718B when they move in the +X-axis direction by        reaction force produced when the wafer stage WST is moved in the        −X-axis direction by a distance corresponding to one shot area        of the wafer W (a distance X₁ shown in FIG. 28).

The Y-axis position of the Y-axis stationary member 722 is not correctedby the Y-axis position correction device.

Scan-exposure is effected on the second shot area SA_(1,2) in a mannersimilar to that of the first shot area SA_(1,1) except that the wafer Wis moved in the +Y-direction.

Subsequent shot areas of the first row are sequentially scan-exposedwhile repeating the stepping operation and the scan-exposure operationdescribed above.

When scan-exposure of the last shot area SA_(1,7) of the first row iscompleted, the stage control system 719 controls the wafer driving unit711, according to instructions from the main control system 721, so thatthe wafer stage WST is moved across the rows to move the wafer W to thescan-exposure starting position for the first shot area SA_(2,9) of thesecond row. Such stepping movement across the rows is made so as tosatisfy the initial conditions of the position and speed at thecompletion of scan-exposure of the shot area SA_(1,7) and the followingthree at-end conditions:

(1″) At the scan-exposure starting position of the shot area SA_(2,9),the wafer W has a velocity component only in the −Y direction, and thevelocity component is set at the predetermined value V_(W).

(2″) At the scan-exposure starting position of the shot area SA_(2,9),the X-axis stationary members 718A and 718B are placed intopredetermined X-axis positions by the first and second X-axis positioncorrection devices. The predetermined X-axis positions are set so as toensure that there is sufficient room for the stroke of the X-axisstationary members 718A and 718B when they are moved in the −X-axisdirection by reaction force produced when the wafer stage WST is movedin the +X-axis direction by a distance corresponding to one shot area ofthe wafer W (distance X₁).

(3″) At the scan-exposure starting position for the shot area SA_(2,9),the Y-axis stationary member 722 is placed into a predetermined Y-axisposition by the Y-axis position correction device. The predeterminedY-axis position is set so as to ensure that there is sufficient room forthe stroke of the Y-axis stationary member 722 when it is moved in the+Y-axis direction by reaction force produced by the movement of thewafer stage WST during scan-exposure of the shot area SA_(2,9) and thestepping movement in the −Y-axis direction from the shot area SA_(2,9)to the next shot area SA_(2,8) and to ensure that there is sufficientroom for the stroke of the Y-axis stationary member 722 when it is movedin the −Y-axis direction by reaction force produced by the steppingmovement of the wafer stage WST in the +Y-axis direction from the shotarea SA_(2,8) to the next shot area SA_(2,7).

Subsequent shot areas of the second row are subjected to scan-exposurein a manner similar to that of the first row, except that scan-exposureprogresses in the −X-axis direction. After that, scan-exposure iseffected on the shot areas of the remaining rows (3-7) in a mannersimilar to that of the first and second rows.

When all the shot areas on the wafer W have been scan-exposed, the waferW is unloaded from the wafer stage WST by an unloader (not shown). Whenunloading the wafer W, the wafer stage WST is moved to an unloadingposition. The movement of the wafer stage WST is controlled in a mannersimilar to that of the above-described reticle alignment. The processesfor the wafer W are thereby completed.

As described above, in the exposure apparatus of the present invention,while the illumination light is being applied to the reticle R, that is,during scan-exposure, when the wafer stage WST is moved along the wafersurface plate 714, the Y-axis stationary member 722 or the X-axisstationary members 718A and 718B serving as a counter stage(countermass) are moved in a direction opposite from the movingdirection of the wafer stage WST. Since most of the reaction force dueto the driving of the wafer stage WST is absorbed, vibration will not becaused and exact exposure is possible. That is, exposure accuracy is notaffected by vibration resulting from reaction force produced due to thedriving of the wafer stage WST.

While illumination light is not applied onto the reticle R, the Y-axisposition correction device and/or the first and second X-axis positioncorrection devices appropriately correct the positions of the Y-axisstationary member 722 or the X-axis stationary members 718A and 718B soas to ensure that there is sufficient room for the stroke of the Y-axisstationary member 722 or the X-axis stationary members 718A and 718Bwhen they are moved in subsequent operations. This shortens the totalspace required for the stroke of the Y-axis stationary member 722 or theX-axis stationary members 718A and 718B, and thereby prevents theexposure apparatus 100 from being of increased size.

In this embodiment, since the X-axis stationary members and the Y-axisstationary member serve as counter stages (countermasses) for absorbingthe reaction force of the wafer stage, it is possible to absorbvibration resulting from the reaction force produced due to the drivingof the wafer stage, without providing another counter stage(countermass) separate from the wafer stage. This allows a smallerfootprint of the entire exposure apparatus. Furthermore, since theX-axis stationary members and the Y-axis stationary member serve ascounter stages (countermasses), they are automatically moved in adirection opposite from the moving direction of the wafer stage byreaction force produced when the wafer stage is moved. Consequently,another driving device for the counter stages is unnecessary, and thereaction force can be easily absorbed.

The positions of the center of gravity in the Y-axis direction and theZ-axis direction of the X-axis stationary member 718A and of the X-axismoving member 720A in the first X-axis motor device coincide withpositions of the points of action of the forces in the X-axis directionacting on the X-axis stationary member 718A and moving member 720A.Furthermore, the positions of the center of gravity in the Y-axisdirection and the Z-axis direction of the X-axis stationary member 718Band of the X-axis moving member 720B in the second X-axis motor devicecoincide with positions of the points of action of the forces in theX-axis direction acting on the X-axis stationary member 718B and movingmember 720B. Furthermore, the positions of the center of gravity in theX-axis direction and the Z-axis direction of the Y-axis stationarymember 722 and of the Y-axis moving member 770 in the Y-axis motordevice coincide with positions of the points of action of the forces inthe Y-axis direction acting on the Y-axis stationary member 722 andmoving member 770.

Accordingly, since during scan-exposure the moving members and thestationary members are moved only in the X-axis direction or the Y-axisdirection by a combination movement therebetween according to the law ofconservation of momentum, the center of gravity of a dynamic systemcomposed of the moving members (stages) and the stationary members incombination is not displaced. Therefore, unbalanced load is not producedand high-precision position control is possible.

The shot areas are arranged in a matrix on the wafer W, and the Y-axisposition of the Y-axis stationary member 722 in the Y-axis motor deviceis corrected by the Y-axis position correction device between thecompletion of exposure of a predetermined row and the start of exposureof a row next to the predetermined row. Since the position of the Y-axisstationary member 722 in the Y-axis motor device is corrected during alinefeed operation in which exposure is suspended for a relatively longperiod, it is possible to prevent vibration and unbalanced load frombeing produced due to the driving of the wafer stage WST as would occurduring scan-exposure. It is also possible to reduce driving force to beapplied to the Y-axis stationary member 722 at the time of correctionand to thereby decrease vibration due to the driving of the Y-axisstationary member 722 to be transmitted to other sections of theexposure apparatus.

While the exposure process of the second layer and subsequent layers ofthe wafer has been described in this embodiment, advantages similar tothose of the above embodiment can also be obtained in exposure of thefirst layer of the wafer that is effected in a manner similar to that ofthe second layer and subsequent layers, except that wafer alignment(search alignment and fine alignment) is not performed.

While the stationary members of the motor devices for moving the waferstage WST are used to absorb reaction force of the wafer stage WST inthe above embodiment, another countermass mechanism may be added.

While absorption of reaction force produced due to the driving of thewafer stage WST has been described in the above embodiment, the presentinvention is also applicable to the driving of the reticle stage RST forholding the reticle R. That is, the position of a counter stage(countermass), which moves in a direction opposite from the drivingdirection of the reticle stage RST, may be corrected to a predeterminedposition when exposure light is not applied. Additionally, the reticlestage may hold a plurality of reticles.

While the exposure apparatus 700 of the above embodiment has only onewafer stage WST, it may have two wafer stages. An exposure apparatus700′ according to a modification of the above embodiment has two waferstages WST1 and WST2, which can independently move in two dimensions, asshown in FIG. 29. In the following description of the exposure apparatus700′, components identical or equivalent to the components of theexposure apparatus 700 are denoted by like numerals, and theirrepetitive explanations will also be omitted.

Referring to FIG. 29, the exposure apparatus 700′ of this modificationis different from the exposure apparatus 700 shown in FIG. 21 in that itincludes: (a) alignment microscopes ALG1 and ALG2 placed at equaldistances from a projection optical system PL, and (b) a wafer drivingunit 811 for moving the wafer stages WST1 and WST2 two-dimensionally.The wafer stages WST1 and WST2 and the wafer driving unit 811 constitutea wafer stage assembly 812 of this modification.

In order to detect the XY positions and the rotations about the Z-axisof the wafer stages WST1 and WST2, the exposure apparatus 700′ alsoincludes: (c) X-axis interferometers 733A and 733B for applying aninterferometric beam to X movable mirrors of the wafer stages WST1 andWST 2, and (d) three Y-axis interferometers (not shown) for applyinginterferometric beams, passing through the center of projection of aprojection optical system PL and the centers of detection of thealignment microscopes ALG1 and ALG2, onto Y-axis movable mirrors of thewafer stages WST1 and WST2. As shown in FIG. 30, an X movable mirror802X and a Y movable mirror 802Y are placed on the upper surface of thewafer stage WST1, and an X movable mirror 803X and a Y movable mirror803Y are similarly placed on the upper surface of the wafer stage WST2.The movable mirrors are represented by a movable mirror 802 and amovable mirror 803 in FIG. 29.

Other sections are similar to those of the above-described exposureapparatus 700.

In the wafer driving unit 811, as shown in FIG. 30, X-axis movingmembers 720A1 and 720A2 similar to the above-described X-axis movingmember 720A are provided for an X-axis stationary member 718A, andX-axis moving members 720B1 and 720B2 similar to the above-describedX-axis moving member 720B are provided for an X-axis stationary member718B. Furthermore, a Y-axis motor device YMA similar to theabove-described Y-axis motor device YM extends between the X-axis movingmembers 720A1 and 720B1, and a Y-axis motor device YMB similar to theabove-described Y-axis motor device YM extends between the X-axis movingmembers 720A2 and 720B2.

The wafer stage WST1 is placed on the upper surface of a moving member770A of the Y-axis motor device YMA, and the wafer stage WST2 is placedon the upper surface of a moving member 770B of the Y-axis motor deviceYMB.

Accordingly, the wafer stage WST1 is moved in the X-axis direction bythe X-axis motor device XMA1 composed of the X-axis stationary member718A and the X-axis moving member 720A1 and the X-axis motor device XMB1composed of the X-axis stationary member 718B and the X-axis movingmember 720B1, and is moved in the Y-axis direction by the Y-axis motordevice YMA composed of the Y-axis stationary member 722A and the Y-axismoving member 770A. In contrast, the wafer stage WST2 is moved in theX-axis direction by the X-axis motor device XMA2 composed of the X-axisstationary member 718A and the X-axis moving member 720A2 and the X-axismotor device XMB2 composed of the X-axis stationary member 718B and theX-axis moving member 720B2, and is moved in the Y-axis direction by theY-axis motor device YMB composed of the Y-axis stationary member 722Band the Y-axis moving member 770B. That is, the wafer stages WST1 andWST2 are two-dimensionally moved in a manner similar to that of theabove-described wafer stage WST.

In the exposure apparatus 700′ of this modification, a concurrentoperation is possible, that is, while shot areas on one of the wafers W1and W2 placed on the wafer stages WST1 and WST2, which can independentlymove in two dimensions, as described above, are sequentially subjectedto scan-exposure similar to that in the above embodiment, the otherwafer is subjected to alignment similar to that in the above embodiment.

During such a concurrent operation, for example, in a case in which thewafer stage WST2 is moved in the X-axis direction by the X-axis motordevices XMA2 and XMB2 while the wafer W1 is scan-exposed by moving thewafer stage WST1 in the Y-axis direction by the Y-axis motor device YMA,the X-axis stationary members 718A and 718B receive a reaction force ina direction opposite from the driving direction of the wafer stage WST2.As a result, if the X-axis position correction device is not operated,the X-axis stationary members 718A and 718B will move in a directionopposite to the driving direction of the stage WST2, which will causethe wafer stage WST1 to move in the X-axis direction identical to themoving direction of the X-axis stationary members 718A and 718B. Thiswould cause the exposure accuracy for the wafer W1 to significantlydeteriorate. In contrast, if the X-axis stationary members 718A and 718Bare prevented from moving by operating the X-axis position correctiondevice, absorption of reaction force (caused by X-direction movement ofthe stage WST2) based on the law of conservation of momentum isimpossible. This causes vibration that affects the wafer stage WST1, andalso deteriorates exposure accuracy for the wafer W1.

Since the Y-axis motor devices YMA and YMB have the above-describedstructure (i.e., they are independent from each other), the Y-axis motordevice for moving one of the wafers in the Y-axis direction does nothave any adverse effect, such as vibration or undesired displacement, onthe other wafer. In other words, when one wafer stage (WST1 or WST2) isdriven in the Y-direction, its stationary member (722A or 722B) can bepermitted to move in order to absorb reaction force, and such movementwill not cause the Y-direction (or X-direction) position of the otherstage (WST2 or WST1) to change.

Accordingly, in the exposure apparatus 700′ of this modification, wafermovement control is executed so that one of the wafers is not moved inthe X-axis direction while the other wafer is being scan-exposed.Therefore, when exposure light EL is applied to the wafer W1, vibrationresulting from the driving of the motor for moving the other wafer isnot transmitted to the wafer stage WST1. This allows high-precisionexposure.

Since exposure and alignment are concurrently performed in the exposureapparatus 700′ of this modification, as described above, throughput canbe improved.

In this modification, movement control may be executed so that, when oneof the wafers moves in the X-axis direction, the other wafer also movesin the same direction by nearly the same distance. This makes itpossible to reduce the distance between the center of projection of theprojection optical system PL and the center of detection of thealignment microscope ALG1 or the alignment microscope ALG2 (so as to belonger than the diameter of the wafer) and to thereby reduce the size ofthe exposure apparatus. Since the size of the stage surface plate 714can also be reduced, production thereof is facilitated.

While the stage device according to the above embodiment of theinvention is applied to the scanning stepper, the invention also isapplicable to a stationary exposure apparatus, such as a stepper thateffects exposure while a mask and a substrate are stationary. In such acase, since reaction force produced when a substrate stage for holdingthe substrate is driven can be absorbed, high-precision exposure issimilarly possible without causing displacement of a transferred image.

The stage device of the invention is also applicable to a proximityexposure apparatus in which a pattern on a mask is transferred onto asubstrate with the mask and the substrate placed in close proximitywithout using a projection optical system therebetween.

The invention is, of course, also applicable not only to an exposureapparatus for use in fabrication of semiconductor devices, but also toan exposure apparatus that transfers a device pattern onto a glass plateso as to produce displays, such as liquid crystal display and plasmadisplays, an exposure apparatus that transfers a device pattern onto aceramic wafer so as to produce thin-film magnetic heads, and an exposureapparatus for use in producing image pickup devices, such as CCDs.

The invention is also applicable not only to microdevices such assemiconductor devices, but also to an exposure apparatus that transfersa circuit pattern onto a glass substrate, a silicon wafer, and the likein order to manufacture a reticle or a mask for use in an opticalexposure apparatus, an EUV (Extreme Ultraviolet) exposure apparatus, anX-ray exposure apparatus, an electron beam exposure apparatus, and thelike. In an exposure apparatus using DUV (Deep Ultraviolet) light, VUV(Vacuum Ultraviolet) light, and the like, a transmissive reticle isgenerally used, and a reticle substrate is made of quartz glass, quartzglass doped with fluorine, fluorite, magnesium fluoride, or quartzcrystal. In the proximity exposure apparatus or the electron beamexposure apparatus, a transmissive mask (a stencil mask or a membranemask) is used. In the EUV exposure apparatus, a reflective mask is used,and a silicon wafer or the like is used as a mask substrate.

The stage device used in the exposure apparatus of the invention is alsowidely applicable to other substrate processing apparatus (for example,a laser apparatus or a substrate inspection apparatus), a samplepositioning device in other precision machines, and a wire bondingdevice.

The exposure apparatus of the invention may employ not only theprojection optical system, but also a charged particle beam opticalsystem, such as an X-ray optical system or an electron optical system.For example, the electron optical system includes an electron lens and apolarizer, and thermoelectron-emitting lanthanum hexaborite (LaB₆) ortantalum (Ta) is used as an electron gun. Of course, the optical paththrough which an electron beam passes is placed in a vacuum. Theexposure apparatus of the invention may use, as exposure light, not onlythe above-described far ultraviolet light or vacuum ultraviolet light,but also soft X-ray EUV light with a wavelength of 5 nm to 30 nm.

For example, the vacuum ultraviolet light includes ArF excimer laserlight and F₂ laser light. Alternatively, a harmonic wave may be usedwhich is obtained by amplifying single-waveform laser light in aninfrared region or a visible region emitted from a DFB semiconductorlaser or a fiber laser by, for example, a fiber amplifier doped witherbium (or both erbium and ytterbium) and wavelength-converting thelaser light into ultraviolet light by using nonlinear optical crystal.

While the projection optical system is of a reduction type in the aboveembodiments, it may be of a 1× (unity) magnification type or of amagnification type.

An illumination unit, a projection optical system, and the like composedof a plurality of lenses is incorporated in the main body of theexposure apparatus so as to provide for optical adjustment. Variouscomponents, such as the X-axis stationary member, the X-axis movingmember, the Y-axis stationary member, the wafer stage, and the reticlestage described above, and other components, are mechanically andelectrically combined and adjusted, and are subjected to totaladjustment (e.g., electric adjustment and operation check), therebyproducing an exposure apparatus of the invention such as the exposureapparatus 100 in the above embodiment. Preferably, the exposureapparatus is produced in a clean room in which the temperature, thelevel of air cleanliness, and the like are controlled.

While the invention has been described with reference to preferredembodiments thereof, it is to be understood that the invention is notlimited to the preferred embodiments or constructions. To the contrary,the invention is intended to cover various modifications and equivalentarrangements. In addition, while the various elements of the preferredembodiments are shown in various combinations and configurations, whichare exemplary, other combinations and configurations, including more,less or only a single element, are also within the spirit and scope ofthe invention.

1. An exposure apparatus comprising: an illumination source that has anon position and an off position; and a stage assembly that moves adevice relative to a stage base so that the device is properlypositioned for one or more operations performed by the exposureapparatus, the stage assembly comprising: a stage that retains thedevice; a stage mover assembly connected to the stage, the stage moverassembly generating reaction forces; a reaction mass assembly coupled tothe stage mover assembly, the reaction mass assembly reducing thereaction forces that are transferred to the stage base; a reaction moverassembly connected to the reaction mass assembly, the reaction moverassembly moving the reaction mass assembly relative to the stage base;and a control system connected to the reaction mover assembly, thecontrol system controlling excitation of the reaction mover assemblyduring the one or more operations for an individual device based uponthe on position and the off position of the illumination source; whereinin the on position, the illumination source directs a beam of lightenergy towards the stage assembly, and in the off position, theillumination source does not direct a beam of light energy towards thestage assembly.
 2. The exposure apparatus of claim 1 wherein the controlsystem controls current to the reaction mover assembly based upon theposition of the illumination source.
 3. The exposure apparatus of claim1 wherein the control system does not direct current to the reactionmover assembly when the illumination source is in the on position. 4.The exposure apparatus of claim 3 wherein the control system directscurrent to the reaction mover assembly when the illumination source isin the off position.
 5. The exposure apparatus of claim 1 wherein thecontrol system directs more current to the reaction mover assembly whenthe illumination source is in the off position than when theillumination source is in the on position.
 6. A device manufactured bythe exposure apparatus of claim
 1. 7. A wafer on which an image has beenformed by the exposure apparatus of claim
 1. 8. An exposure apparatusthat forms images on a device, the exposure apparatus comprising: astage assembly that moves a device relative to a stage base so that thedevice is properly positioned for one or more operations performed bythe exposure apparatus, the stage assembly comprising: a stage thatretains the device; a stage mover assembly connected to the stage, thestage mover assembly generating reaction forces; a reaction massassembly coupled to the stage mover assembly, the reaction mass assemblyreducing the reaction forces that are transferred to the stage base; areaction mover assembly connected to the reaction mass assembly, thereaction mover assembly moving the reaction mass assembly relative tothe stage base; and a control system connected to the reaction moverassembly, the control system controlling excitation of the reactionmover assembly during the one or more operations for an individualdevice based upon a status of the operation for forming images on theindividual device.
 9. The exposure apparatus of claim 8 wherein thestage mover assembly moves the stage with two degrees of freedom and thereaction mass assembly is adapted to reduce the reaction forces in thetwo degrees of freedom that are transferred to the stage base.
 10. Theexposure apparatus of claim 8 wherein the stage mover assembly moves thestage with three degrees of freedom and the reaction mass assembly isadapted to reduce the reaction forces in the three degrees of freedomthat are transferred to the stage base.
 11. The exposure apparatus ofclaim 8 wherein the reaction mover assembly adjusts the position of thereaction mass assembly relative to the stage base with one degree offreedom.
 12. The exposure apparatus of claim 8 wherein the reactionmover assembly adjusts the position of the reaction mass assemblyrelative to the stage base with two degrees of freedom.
 13. The exposureapparatus of claim 8 wherein the reaction mover assembly adjusts theposition of the reaction mass assembly relative to the stage base withthree degrees of freedom.
 14. The exposure apparatus of claim 8 whereinthe reaction mass assembly includes an X reaction component and a Yreaction component that are coupled to the stage mover assembly, the Xreaction component moves relative to the Y reaction component along an Xaxis and the X reaction component and the Y reaction component moveconcurrently along a Y axis relative to the stage base.
 15. The exposureapparatus of claim 14 wherein the reaction mover assembly adjusts theposition of the X reaction component relative to the Y reactioncomponent along the X axis.
 16. The exposure apparatus of claim 15wherein the reaction mover assembly adjusts the position of the Yreaction component and the X reaction component relative to the stagebase along the Y axis.
 17. The exposure apparatus of claim 16 whereinthe reaction mover assembly adjusts the position of the Y reactioncomponent and the X reaction component relative to the stage base abouta Z axis.
 18. The exposure apparatus of claim 14 wherein the X reactioncomponent includes a first X reaction mass and a second X reaction massthat move independently along the X axis relative to the Y reactioncomponent and the reaction mover assembly adjusts the position of the Xreaction masses relative to the Y reaction component.
 19. The exposureapparatus of claim 8 wherein the control system directs current to thereaction mover assembly between the forming of each image on the deviceand does not direct current to the reaction mover assembly during theforming of each image on the device.
 20. The exposure apparatus of claim8 wherein the control system directs current to the reaction moverassembly between the forming of each row of images on the device anddoes not direct current to the reaction mover assembly during theforming of each row of images on the device.
 21. The exposure apparatusof claim 8 wherein the control system directs current to the reactionmover assembly between each scan of the device and does not directcurrent to the reaction mover assembly during each scan of the device.22. The exposure apparatus of claim 8 wherein the control system directscurrent to the reaction mover assembly between each device manufacturedby the exposure apparatus and does not direct current to the reactionmover assembly during the manufacture of each device.
 23. The exposureapparatus of claim 8 wherein the control system directs more current tothe reaction mover assembly between the forming of each image on thedevice than during the forming of each image on the device.
 24. Theexposure apparatus of claim 8 wherein the control system directs morecurrent to the reaction mover assembly between the transfer of each rowof images onto the device than during the transfer of each row of imagesto the device.
 25. The exposure apparatus of claim 8 wherein the controlsystem directs more current to the reaction mover assembly between eachscan of the device than during each scan of the device.
 26. The exposureapparatus of claim 8 wherein the control system directs more current tothe reaction mover assembly between each device manufactured by theexposure apparatus than during the manufacture of each device.
 27. Anexposure apparatus for forming images on a device, the exposureapparatus comprising: an illumination source having an on position andan off position, in the on position, the illumination source directs abeam of light energy, in the off position, the illumination source doesnot direct a beam of light energy; a stage base; a stage assembly thatmoves the device relative to the stage base, the stage assemblyincluding (i) a stage that retains the device, (ii) a stage moverassembly that moves the stage relative to the stage base, the stagemover assembly generating reaction forces, (iii) a reaction massassembly coupled to the stage mover assembly, the reaction mass assemblyreducing the reaction forces that are transferred to the stage base,(iv) a reaction mover assembly that moves the reaction mass assemblyrelative to the stage base, and (v) a control system connected to thereaction mover assembly, the control system controlling excitation ofthe reaction mover assembly based upon the position of the illuminationsource.
 28. The exposure apparatus of claim 27 wherein the controlsystem does not direct current to the reaction mover assembly when theillumination source is in the on position.
 29. The exposure apparatus ofclaim 28 wherein the control system directs current to the reactionmover assembly when the illumination source is in the off position. 30.The exposure apparatus of claim 27 wherein the control system directsmore current to the reaction mover assembly when the illumination sourceis in the off position than when the illumination source is in the onposition.
 31. The exposure apparatus of claim 27 wherein the controlsystem directs current to the reaction mover assembly between theforming of each image on the device and does not direct current to thereaction mover assembly during the forming of each image on the device.32. The exposure apparatus of claim 27 wherein the control systemdirects current to the reaction mover assembly between the forming ofeach row of images on the device and does not direct current to thereaction mover assembly during the forming of each row of images on thedevice.
 33. The exposure apparatus of claim 27 wherein the controlsystem directs current to the reaction mover assembly between each scanof the device and does not direct current to the reaction mover assemblyduring each scan of the device.
 34. The exposure apparatus of claim 27wherein the control system directs current to the reaction moverassembly between each device manufactured by the exposure apparatus anddoes not direct current to the reaction mover assembly during themanufacture of each device.
 35. The exposure apparatus of claim 27wherein the control system directs more current to the reaction moverassembly between the forming of each image on the device than during theforming of each image on the device.
 36. The exposure apparatus of claim27 wherein the control system directs more current to the reaction moverassembly between the forming of each row of images on the device thanduring the forming of each row of images on the device.
 37. The exposureapparatus of claim 27 wherein the control system directs more current tothe reaction mover assembly between each scan of the device than duringeach scan of the device.
 38. The exposure apparatus of claim 27 whereinthe control system directs more current to the reaction mover assemblybetween each device manufactured by the exposure apparatus than duringthe manufacture of each device.
 39. The exposure apparatus of claim 27wherein the reaction mover assembly adjusts the position of the reactionmass assembly relative to the stage base with at least one degree offreedom.
 40. The exposure apparatus of claim 27 wherein the reactionmover assembly adjusts the position of the reaction mass assemblyrelative to the stage base with two degrees of freedom.
 41. The exposureapparatus of claim 27 wherein the reaction mover assembly adjusts theposition of the reaction mass assembly relative to the stage base withthree degrees of freedom.
 42. A device manufactured by the exposureapparatus of claim
 27. 43. A wafer on which an image has been formed bythe exposure apparatus of claim
 27. 44. A method for manufacturing anexposure apparatus that forms images on a device, the exposure apparatuscomprising an illumination source that has an on position and an offposition, and a stage assembly that moves the device relative to a stagebase so that the device is properly positioned for one or moreoperations performed by the exposure apparatus, the method comprisingthe steps of: providing an illumination source; and providing a stageassembly, the step of providing the stage assembly comprising the stepsof: providing a stage that retains the device; connecting a stage moverassembly to the stage that moves the stage relative to the stage base,the stage mover assembly generating reaction forces; coupling a reactionmass assembly to the stage mover assembly, the reaction mass assemblyreducing the reaction forces that are transferred to the stage base;connecting a reaction mover assembly to the reaction mass assembly, thereaction mover assembly moving the reaction mass assembly relative tothe stage base; and providing a control system that is connected to thereaction mover assembly and controls excitation of the reaction moverassembly during the one or more operations for an individual devicebased upon the on position and the off position of the illuminationsource; wherein in the on position, the illumination source directs abeam of light energy towards the stage assembly, and in the offposition, the illumination source does not direct a beam of light energytowards the stage assembly.
 45. The method of claim 44 wherein the stepof providing a control system includes the step of providing a controlsystem that controls current to the reaction mover assembly based uponthe position of the illumination source.
 46. The method of claim 44wherein the step of providing a control system includes the step ofproviding a control system that does not direct current to the reactionmover assembly when the illumination source is in the on position. 47.The method of claim 46 wherein the step of providing a control systemincludes the step of providing a control system that directs current tothe reaction mover assembly when the illumination source is in the offposition.
 48. The method of claim 44 wherein the step of providing acontrol system includes the step of providing a control system thatdirects more current to the reaction mover assembly when theillumination source is in the off position than when the illuminationsource is in the on position.
 49. The method of claim 44 wherein thestep of providing a control system includes the step of providing acontrol system that directs current to the reaction mover assemblybetween the forming of each image on the device and does not directcurrent to the reaction mover assembly during the forming of each imageon the device.
 50. The method of claim 44 wherein the step of providinga control system includes the step of providing a control system thatdirects current to the reaction mover assembly between the forming ofeach row of images on the device and does not direct current to thereaction mover assembly during the forming of each row of images on thedevice.
 51. The method of claim 44 wherein the step of providing acontrol system includes the step of providing a control system thatdirects current to the reaction mover assembly between each scan of thedevice and does not direct current to the reaction mover assembly duringeach scan of the device.
 52. The method of claim 44 wherein the step ofproviding a control system includes the step of providing a controlsystem that directs current to the reaction mover assembly between eachdevice manufactured by the exposure apparatus and does not directcurrent to the reaction mover assembly during the manufacture of eachdevice.
 53. The method of claim 44 wherein the step of providing acontrol system includes the step of providing a control system thatdirects more current to the reaction mover assembly between the formingof each image on the device than during the forming of each image on thedevice.
 54. The method of claim 44 wherein the step of providing acontrol system includes the step of providing a control system thatdirects more current to the reaction mover assembly between the transferof each row of images onto the device than during the transfer of eachrow of images to the device.
 55. The method of claim 44 wherein the stepof providing a control system includes the step of providing a controlsystem that directs more current to the reaction mover assembly betweeneach scan of the device than during each scan of the device.
 56. Themethod of claim 44 wherein the step of providing a control systemincludes the step of providing a control system that directs morecurrent to the reaction mover assembly between each device manufacturedby the exposure apparatus than during the manufacture of each device.57. A method of making a wafer utilizing the exposure apparatus made bythe method of claim
 44. 58. A method of making a device utilizing theexposure apparatus made by the method of claim 44.